Technical Information
geral@ota-abrasivos.pt
Tel +351 226 178 423 / 443
Call to national fixed network
What are the main abrasive families?
Abrasives are used for various purposes and can be in solid or liquid form (actually grains in compounds). They cover functions from cutting and grinding to high-gloss polishing. In solid form, they are generally presented in the following formats.
Bonded abrasives – constitutes a solid mixture of abrasive grains with a binder, normally rigid, coming in many forms: discs (the most common), grinding wheels, wheels, blocks, plates, etc. The binder can also be flexible or elastic, using rubber or polyurethane.
Coated Abrasives – a coated abrasive represents an abrasive fixed to a support material, usually paper, cloth or even sponge, flexible by nature. Traditional sandpaper falls into this family. A resin is normally applied to the support into which the abrasive grain is integrated.
Non-woven abrasives – These products are often referred to as “Scotch®” or three-dimensional abrasives. The abrasive grains are bonded to flexible nylon fibres saturated with abrasive grains. This “open-weave” construction provides a continuous supply of new grains as the fibre and old grains wear out. Non-woven products are adaptable to contours. The abrasive grains are distributed throughout the thickness of the material, exposing the grain even more during normal wear. This ensures consistent performance throughout the product’s lifespan, can be used on both sides, and never loses maximum abrasive performance. Non-woven abrasives have a very high mineral content. The open non-woven structure minimises the tendency to clog. Non-woven abrasives can be used wet or dry or in conjunction with polishing fluids. Non-woven abrasives are ideal for applications involving low cutting speed and low contact pressure.
Felts and Cloths – are products intended for the final polishing of parts, and are normally used with soaps, compounds, or other polishing fluids.
What are the different types of most common abrasive grains?
Aluminium oxide (AO or Alox)
Aluminium oxide is the most common and typically least expensive grain. Provides a good starting point for most metal applications, such as iron, carbon steel, alloy steel, hard bronze and all woods. It is the ideal solution when toughness is desired, that is, the ability to resist fracturing. Aluminium oxide is generally brown or reddish, but may have other colours (blue, green, or yellow), which generally indicates the presence of additional coating layers for cooling, lubrication or to prevent sogginess. It is durable, with resistant cutting edges, tending to lose its edges during use. Aluminium oxide is available in a wide range of grains and is the type of abrasive with the most variants.
Silicon carbide (SiC)
Silicon carbide is the hardest and sharpest of the minerals used in coated abrasives. Its hardness and very sharp shape make this abrasive ideal for sanding non-ferrous metals (aluminium, brass, bronze, magnesium, titanium alloys, etc.) or even cast iron, not too hard, glass, paints, rubber, plastics, fibrous wood, and other relatively soft materials that do not require great pressure when cutting. SiC typically has a black or grey colour. Its grains are friable, breaking which continually exposes new cutting edges and allows rapid removal of the material. It is more aggressive than the AO but, as it wears more quickly, it presents a more pronounced wear curve over time.
Zirconium (Z or Zr)
Zirconium (Zirconia Alumina, Zirc or Zirconium – Zr) is suitable for coarse to medium particle size applications in metal, being an excellent choice for demanding applications, for example in stainless steel. The Zr is usually blue in colour. It works best under high pressure, which is necessary for the grain to break, exposing new sharp edges. It is a type of abrasive that has large fracture planes and self-sharpens during cutting. Zr is available in limited particle sizes and on strong supports.
Ceramic (Cer)
Ceramic aluminum oxide abrasives (Ceramic Alumina – Cer) have the longest life and fastest cut rate of all coated abrasives. They are the latest introduction in abrasive grains and present maximum performance, providing an aggressive and consistent cut under moderate to high pressure, as they break down into microparticles, keeping the abrasive surface permanently sharp. Cer is the most expensive of all abrasives and is generally red or orange in color. It is mainly used in metal applications, especially hard ones, such as stainless steel, or alloys with a high content of nickel and cobalt. Cer grains are available in a larger granulometry than Zr but much less extensive than Alox and SiC, not reaching grains as fine as these, which is natural, as in this range the polishing capacity becomes more important and less the material removal.
Compact Grains (Cmp)
Coated abrasives with compact grains are therefore very different from conventional flexible abrasives, constituting a cluster or agglomeration of several abrasive grains of the same size. In simple terms, the product has multiple layers of the same grain, compared to just one layer in a conventionally coated abrasive product. As one layer of abrasive grain wears away, another layer is exposed. The tight grain construction results in less load, longer life, and a very constant finish over the lifetime. Mainly used in metal applications, namely in automated grinding applications on stainless steel and light high alloy steels. They are typically more expensive than the conventional coated abrasives.
How is the particle size of abrasives classified?
How is the particle size of abrasives classified?
There are several standards for measuring the particle size of abrasives. The best known is FEPA – Fédération Européenne des Fabricants de Produits Abrasifs (Federation of European Abrasive Producers).
FEPA distinguishes between sanding grits, i.e. for use on substrates (FEPA P), and agglomerated grits on abrasive parts / bonded abrasives, namely grinding wheels or abrasive wheels (FEPA F).
Grain sizes are defined by the number of lines per inch (25.4 mm) on a sieve, or, in more simplistic terms, how many grains would fit, juxtaposed, and aligned, in one inch. For example, for a 120 grit abrasive, there would be 120 lines/inch on the sieve, or 120 juxtaposed and aligned grains per inch would fit. This means that the lower numbers (16, 24, …) correspond to the coarser and more aggressive grits, intended for grinding, and the higher numbers (1000, 1200, …) correspond to the finest grits, intended for final polishing.
The following table shows the equivalence between the various granulometric conventions. OTA uses, as a rule, the FEPA convention in which the grit number is preceded by a P. This is an important guarantee of quality, as the user knows, with complete precision, which grit he is using. Some manufacturers, in some exceptionally fine products, present the particle size directly in microns and others present their own particle size with conversion tables. The following table also includes the grits typically available on the market for the main types of coated abrasives: Alox, SiC, Zr, Cer and Cmp. Please note that this table is merely indicative.
What are the extra coatings most used in coated abrasives?
It is common for coated abrasives to have surface treatments to improve their performance. The main ones are as follows.
Top Size Layer
The Top Size Layer is recommended for dry grinding of stainless steels and non-ferrous metals. Thanks to the additional layer with its grinding-inducing additives, cutting performance is improved while the temperature in the contact area is reduced. Furthermore, the lifespan of the abrasive increases substantially.
Stearate Layer
The Stearate anti-adhesive layer is mainly used to work non-ferrous metals, for example aluminium, preventing particle adhesion and, therefore, clogging/sogginess of the abrasive. Increases the useful life of the abrasive.
Antistatic Layer
Abrasives with an antistatic layer are mainly used for working wood or other non-conductive materials. Normally its support is supplemented with electrically conductive substances that ensure that electrical charges can be safely discharged through the abrasive to the equipment.
They prevent the buildup of an electrostatic charge so that sanding dust does not adhere to the workpiece or machine. It aims to prevent the abrasive from blocking and extends its useful life. Most wood finishing products have this treatment, and some even include an anti-static finish on the abrasive side through the inclusion of conductive substances (for example, graphite) in the own binding resins, improving the effect.
Note: this treatment, although an extra, does not correspond to the graphic representation above, as it does not constitute a coating layer.
What types of support are used in flexible abrasives?
There is a wide variety of solutions that support coated abrasives.
Paper
Paper supports have different weights, are designated by letters, and are available for different applications. Standard paperweights are indicated by a letter that is sometimes included in the finished product code. The lighter the support, the greater the degree of flexibility, the heavier the paper, the greater the resistance to breaking. The nature of each paper (density, thickness, flexibility, etc.) varies from manufacturer to manufacturer, including the treatments applied to it. For example, a waterproofing layer intended to withstand wet abrasive applications changes the characteristics of the substrate.
|
Paper |
Weight (g/m2) |
Notes |
|
A |
70-80 |
Lightweight and flexible, A paper is mainly used for manual operation with dry and wet finishing. In the latter case, the paper is waterproofed and gains a little more weight. It is used in all particle sizes, but especially above (finer) P80. |
|
B |
90-105 |
Similar to A paper, but can support coarser grains than P80. |
|
C |
110-125 |
This medium and light paper is used when some flexibility and strength are required. Stronger and less flexible than papers A and B, this support is also chosen for manual work (dry or wet) and for use in small portable sanders. This support is used with fine and medium grits. |
|
D |
130-160 |
Stronger and less flexible than C paper. This paper is still chosen for hand sanding and for use in portable sanders. It is used on grits that are already relatively coarse P36 to P80. |
|
E |
220-250 |
This support is no longer used in manual applications, but is mainly used in rolls, belts, and discs, where high resistance to breakage and cutting is required. |
|
F |
300 |
It is the most resistant and least flexible standard paper support used on the market. Used on belts, rolls, and discs that require great resistance, for example on large belts. |
|
G |
400 |
It is a very heavy paper, rarely used. |
Cloth
Cloth backings are more durable than paper, offer greater tear resistance and tolerate continuous bending, remaining flexible during use, but are more expensive. They can be made of cotton, polyester, or a mixture of both (polycotton) (PA). The body/thickness is also referenced by letters, which depend largely on each manufacturer. Typical references are as follows.
|
Cloth |
Notes |
|
JJF |
Normally in cotton. It is a hyper flexible support. It is relatively rare and applies to very fine grains. It may correspond to a JF screen from another manufacturer. |
|
JF |
Normally in cotton, but also in a polyester mix (PA), when you want to give it more mechanical resistance. It is the most flexible support available on the market, with fine and medium grains. In practice, it constitutes a more flexible variant of the J reference. |
|
J |
It is one of the market references and its name comes from the word “jeans”. It is a light and flexible cloth, used where surface finish and uniformity are more important than material removal. It is ideal for finishing, where flexibility and conformity are essential, such as contour work, especially curved surfaces. |
|
X |
Stronger and more rigid when compared to J screen, this support is used in products designed for medium and thick grains and material removal applications and finishing with fine grains. It is one of the standard backings for all manufacturers. |
|
Y |
Stronger and more resistant to breakage and cutting, it is a backing used in products designed for severe applications, normally in belts. It is generally made of polyester to guarantee greater mechanical resistance. It is, along with the J and X screens, another reference on the market. |
|
H |
Stronger and more resistant than Y screens, it has less flexibility. It is relatively rare. |
|
Z |
The strongest and most resistant of cloths. It’s rare. |
Regarding these references, there are several variants on the market:
JF cloths also have designations such as JJ, F or JFlex.
There are slightly more flexible X cloths, which manufacturers refer to as XJ, XF or XFlex.
There are intermediate screens, between the X and Y cloths, which are referred to as XY or YX.
Some manufacturers use reinforced Y cloths, which they distinguish by designating them YY. Others may eventually designate them as H.
Combination
It constitutes a backing combining, by lamination, fabric, and rigid paper (E or F) and is used where mechanical resistance to rupture and breaking/folding is a determining requirement. It is mainly used in large calibrating belts with coarse grits, for chipboard/MDF.
Film
Polyester film is used as a backing for precision polishing products. It is most often used for abrasive belts and discs for orbital sanders. Film is more durable, mechanically, and chemically resistant to attacks than paper, but more expensive and more difficult to recycle. It can be used wet or dry. It is typically intended for very fine grains, above P800, to ensure superior abrasive surface uniformity and better finish quality.
Fiber
Fiber is a hard and durable material with great mechanical strength, which can provide enough flexibility for some applications. Typically, the fiber is made up of several layers of paper bound by resin. Its thicknesses can vary between 0.6 and 0.8 mm and has the greatest resistance of coated abrasive backings. It is exclusively used to make resin fiber discs. It often has a top size layer.
What types of finishes are used on flexible abrasive supports?
The strict backing/abrasive combination must often be complemented with a finishing to give it flexibility, additional rigidity or, simply, to allow its use with certain tools or equipment. The following finishings can be used simply applied to the backing or with different combinations of them.
Velour (Vel) – is the most common situation and is intended to allow the use of discs or sheets on equipment or pads with a Velcro® type system to allow easy and quick operation. Velour can come in a wide range of weights and resistances.
Adhesive – typically PSA type, which allows a similar use to Vel, although it is intended for specific needs. Also typically used on discs and sheets.
Foam – to provide cushioning to the coated abrasive, normally with a paper backing. It can have different thicknesses and elasticities.
Reinforcements – of the most varied nature, both in paper and synthetic material, intended to provide more resistance or rigidity to the backing. It is not of general application, being designed for special situations.
How should I store abrasive products?
The best way to ensure that abrasive products maintain maximum performance and lifespan is to store them properly. The bonding and backing materials used in abrasives are sensitive to changes in temperature and humidity.
Abrasives must be stored in environments with a temperature between 15ºC and 25ºC and a relative humidity between 35% and 50% and protected from solar radiation and heat sources.
Products must be kept in their packaging until ready for use. Some of them even have well-defined expiration dates.
I like the abrasive I’m using, but I don’t see it on the OTA website. How can I find it?
We suggest that you take the references from the product you are using, or want, and contact our commercial department at (+351) 226 178 423 or geral@ota-abrasivos.pt.
We will be happy to help you find the best choice.
Belts and Wide Belts
What are abrasive belts?
Abrasive belts are continuous loops of abrasive material used in machinery for sanding, grinding, polishing, or finishing surfaces. These belts are mounted on machines like belt sanders or grinding machines to remove material, smooth surfaces, or achieve specific finishes on a variety of materials such as wood, metal, plastics, and composites.
How do I choose the right abrasive belt for my project?
The defining properties of a belt are: belt size, grain type, grain size, backing type, and backing weight.
Choosing the right abrasive belt depends on the following factors:
• Material type: Select a belt suitable for the material you’re working with (wood, metal, plastic, etc.).
• Abrasive material: Common abrasives include aluminium oxide (for general use), silicon carbide (for non-ferrous metals and plastics), and zirconia alumina (for tough materials like stainless steel).
• Grit size: Coarse grits (e.g., 24-60) are ideal for heavy material removal, while finer grits (e.g., 120-400) are used for finishing and polishing.
• Belt size: Ensure that the belt matches the dimensions required by your machine
• Joint type: it is best to contact us in this matter or take the selection according to the criteria of the respective manufacturer.
What are the measurements for an abrasive belt?
Belts are measured in two dimensions width and length (perimeter).
OTA adopts the convention length x with, always in mm. Nevertheless, the most common is the reverse: width x length.
What are the most common belt dimensions?
There are many widths, which combine with many lengths, which is why they are divided into families:
• Narrow belts (file belts): typically, between 6 and 50 mm wide.
• Normal belts: typically, between 50 and 300 mm wide.
• Calibrating or wide belts: typically, between 600 and 1650 mm wide.
• Segmented belts: widths above 1650 mm, which require a special manufacturing process.
What are the most common betl lengths?
Belt length depends on the equipment where it will be used.
Available lengths are immense, ranging from about 50 mm to over a dozen meters.
Length is typically associated with width: very narrow and very long belts are uncommon, as are the reverse (very wide and very short).
Does OTA have standard belt sizes?
OTA’s belt approach is made-to-order, meaning it produces belts to order. Therefore, there are no standard sizes, enabling us to manufacture belts for virtually any length x width combination.
This flexibility in terms of dimensions is complemented by a wide variety of abrasives, grits, backings, and qualities, so we can supply virtually any type of belt required for your application.
What is a wide belt?
A wide abrasive belt is a type of continuous belt (i.e., ring-shaped) sandpaper used in calibrating machines for precise grinding of large surfaces, primarily wood, but also metals and other materials.
The calibrating machine’s function is to level and give uniform thickness to workpieces (especially wood). It differs from a standard sander because it offers greater precision, dimensions, and controlled material removal capacity.
In practical terms, it’s simply a belt with a wider width than usual, which can vary between 600 mm (purely conventional) and 1650 mm, dictated by the width of the rolls from which they are manufactured.
What are file belts?
File belts are a type of abrasive belt that is primarily used for precise and fine finishing tasks, typically in small spaces or for detailed work. They are often used with file belt sanders, which are specialized tools designed for finer, more controlled sanding or grinding applications.
Key Features of File Belts:
• Narrow and Flexible: File belts are generally narrower than traditional sanding belts, which allows for more precision in sanding and finishing operations. They can fit into tight spaces and be maneuvered more easily for detailed work.
• Flexible Backing: The backing material of file belts is usually flexible to provide more control during sanding and to follow the contours of the workpiece better.
• Available in Different Grains and Grits: Like other abrasive belts, file belts come in a range of grit sizes, from coarser grits (for material removal) to finer grits (for polishing or finishing), grains (Alox, SiC, Zr and Cer) and materials, typically coated abrasives or SCM.
Common Uses of File Belts:
• Metalworking: They are used to smooth out weld seams, deburr edges, or finish small metal parts.
• Woodworking: File belts are sometimes used for sanding small or delicate wooden pieces, such as trim, molding, or intricate designs.
• Plastic and Composite Materials: They are used to achieve a smooth finish on plastic or composite parts, especially where precision is needed.
Types of File Belt Sanders:
• Handheld File Belt Sanders: These are lightweight, portable tools designed for manual operation, often used for more detailed, precise sanding.
• Stationary File Belt Sanders: Larger versions may be used in industrial or commercial settings for repetitive tasks that require fine finishing.
What are the most common file belts widths?
The most common widths for file belts are typically designed for precision sanding and finishing, and they vary based on the specific application and the respective machine.
Here are the most commonly used widths:
• 6 a 8 mm (1/4”): common in precision polishing processes.
• 12-15 mm (1/2”): This is one of the most common widths for file belts, particularly for finer, detailed work. It is ideal for precision sanding in tight or narrow spaces, such as removing burrs or smoothing edges on small parts.
• 20mm (3/4”): A slightly wider belt that offers a good balance between detailed work and the ability to cover more surface area. It’s often used for tasks that require a bit more sanding surface, like polishing small metal or wood components.
• 25mm (1”): This width is often used for general-purpose file sanding, providing more abrasiveness and efficiency for slightly larger tasks without compromising the precision needed for smaller workpieces.
• 50 mm (2”): Although less common for fine details, these belts are used for broader finishing tasks that require more sanding power. It’s useful for achieving smoother finishes on medium-sized parts, especially when working with metal or wood.
What are the grit ranges of abrasive belts?
The grit size on an abrasive belt determines its coarseness:
• Coarse grits (16-60): Best for aggressive material removal and rough sanding.
• Medium grits (80-120): Ideal for general-purpose sanding and intermediate finishing.
• Fine grits (150-400): Used for polishing, finishing, and smoothing surfaces.
• Extra fine grits (600+): For ultra-fine finishing and polishing, often used on metals finishes.
How does grain size affect finish?
The larger the number (grain size), the rougher the finish.
What types of abrasive materials are used in abrasive belts?
• Aluminium Oxide (Alox): A versatile, long-lasting abrasive used for general-purpose sanding and grinding.
• Silicon Carbide (SiC): Harder and sharper, ideal for sanding non-ferrous metals, glass, ceramics, and plastics.
• Zirconia (Zr): Durable and ideal for heavy grinding on tough materials like steel and stainless steel.
• Ceramic (Cer): High-performance material for extreme material removal and tough metalworking tasks.
What is the best general purpose abrasive grain?
Aluminium oxide (Alox) is offered in very coarse to very fine grain sizes for a broad array of finishes and general purpose applications.
Can I use the same abrasive belt for different materials?
While some abrasive belts can work across multiple materials, it’s best to use a belt designed for the specific material to achieve optimal results and prolong the life of the belt.
For instance, a silicon carbide belt is better for non-ferrous metals and plastics, while aluminium oxide is better suited for wood and general-purpose use.
Where do I use zirconia grains?
You use zirconia (Zr) on metals, as well with less cut and performance versus ceramic grains.
Where do I use ceramic grains?
Ceramic (Cer) grains are mostly used on stainless steel or other high alloy metals for removing material.
What belt should I use for woodworking?
Cloth or paper backed aluminium oxide open coat materials work well on wood.
What are the most common backing types for abrasive belts?
The backing of an abrasive belt is the material that provides the structural support for the abrasive grains, allowing the belt to maintain its shape and strength during use.
The type of backing used in an abrasive belt plays a crucial role in its flexibility, durability, and suitability for different applications.
Here are the most common types of backings for abrasive belts:
1. Cloth Backing
• Description: Cloth backings are the most commonly used and are made from woven fabrics, typically cotton or polyester. These backings provide flexibility, strength, and resistance to wear.
• Characteristics:
– Highly flexible, which allows for better conforming to the shape of the workpiece.
– Ideal for applications where the belt needs to bend or flex (e.g., sanding contours or curved surfaces).
– Offers good tear resistance and durability, especially when used in heavy-duty applications.
• Types of Cloth Backing:
– Cotton: Used in belts for general-purpose applications.
– Polyester: More durable and tear-resistant, often used for heavy-duty or high-performance applications.
– Poly/cotton blends: Combining both materials for enhanced performance and flexibility.
– Applications: Woodworking, metalworking, and polishing.
2. Paper Backing
• Description: Paper backings are generally made from a sheet of kraft paper or other paper materials and are often used in light- to medium-duty applications.
• Characteristics:
– Less durable and flexible compared to cloth backings.
– More rigid, which makes them less suitable for sanding curved or contoured surfaces.
– Typically used for finer sanding tasks or where high precision is required.
– Applications: Fine sanding, finishing, and polishing tasks on wood, metal, and plastic.
3. Film Backing
• Description: Film backings are made from a thin, flexible plastic film (such as polyester or other polymer materials). This type of backing is durable, tear-resistant, and provides a smooth, consistent surface for the abrasive grains.
• Characteristics:
– Extremely durable and resistant to tearing and stretching.
– Provides a very smooth and flat surface, which helps maintain the uniformity of the abrasive surface.
– Offers more consistent performance compared to paper or cloth, particularly for precision applications.
– Excellent for high-performance tasks requiring minimal stretch and maximum control.
– Applications: Precision sanding, polishing, and grinding, especially in the automotive, aerospace, and electronics industries.
4. Non-Woven Synthetic Fiber Backing
• Description: Made from synthetic fibers, this type of backing is often used for specialized abrasive products like “scotch-brite®” or non-woven abrasives.
• Characteristics:
– Offers a softer, more flexible finish compared to other backings.
– Ideal for tasks that require light abrasive action, like cleaning, polishing, or surface finishing without removing a lot of material.
• Applications: Cleaning, finishing, light sanding, and surface preparation.
Summary of Backing Types:
• Cloth: Flexible and durable, good for heavy-duty and curved surface work (e.g., woodworking, metalworking).
• Paper: Rigid, best for fine finishing and light to medium-duty sanding (e.g., fine sanding wood or metal).
• Film: Smooth, tear-resistant, best for precision and high-performance tasks (e.g., automotive and aerospace).
• Non-Woven Fiber: Soft and flexible, used for light abrasive tasks like cleaning or surface conditioning.
Each type of backing has specific advantages depending on the type of task you are performing. For heavy-duty applications, cloth backings are often preferred. For precise finishing work, film and paper backings are typically used.
What types of paper backings are there?
Paper backings are offered from A weight through F weight.
Flexibility and durability are the differences. A weight is the most flexible and least durable, and F weight is the least flexible and most durable.
What types of cloth backings are there?
The different backings are cotton, polyester, and poly cotton.
Flexibility, durability and water resistance are the key differences:
Cotton – more flexible for the same weight, less tear-resistant, non-waterproof
Polyester – less flexible for the same weight, more tear-resistant, waterproof
Polycotton – in de middle of both, waterproof.
Concerning flexibility, it goes from the most flexible (JJ, JF or H) to the harder (YY or Z).
What types of abrasive belt joints are there?
Joints are used to connect the two ends of the belt into a continuous whole. The joint plays a crucial role in the belt’s durability, performance, and suitability for specific applications.
Joints are defined by the angle and the type of bonding/fixing of the two ends of the belt.
– Regarding the angle:
• The most common are 67º and 55º.
• The less common are 90º and 45º.
Decreasing the angle also tends to reduce the effect on the part of any difference in thickness at the joint and slightly increase the belt’s tensile strength. However, its cost increases due to its greater length and increased sandpaper waste.
– When it comes to fixing the ends, OTA uses the following alternatives:
T1 (Normal – N) – This is a joint in which the two ends of the belt overlap, sanding the bottom and top of each to minimize the increase in thickness in the joint area. This is the most common joint.
T2 (Stripped – D) – This is the same as the Type 1 joint, with additional abrasive stripping applied to the overlapping area to ensure that the joint does not protrude during the sanding process.
T3 (Butt-to-Butt – TT) – This is a joint in which the two ends are butted together and a reinforced polyester tape is used to secure the two ends to the back of the belt, similar to a standard adhesive tape.
T4 (TTD) – This joint is similar to Type 3, with additional abrasive stripping in the joint area to ensure no protrusion during the sanding process.
T5 (TTR) – This joint is similar to Type 3, except that the bonding is performed at the front of the belt, requiring abrasive stripping at both ends of the belt.
T1 and T3 joints are the most common, with T1 being the most economical.
T3 tends to be recommended when the belt is subjected to very high stresses, especially on cloth and heavy-grain belts.
Type 5 is used for very fine polishing processes on paper or flexible cloth belts.
T2 and T4 cover specific cases when similar types (T1 and T3) are not suitable.
How to choose the right joint?
The type of joint you choose for your abrasive belt depends on the application and the stress it will be subjected to.
Paper belts typically use Type 1 joints, and cloth belts use Type 3 joints, but there are a wide variety of situations, combined with the respective angles.
What information is on the back of a belt?
The back of a belt should have the grit size and product number information.
How do I properly install an abrasive belt on my machine?
To install an abrasive belt:
• Turn off and unplug the machine for safety.
• Release the tension on the existing belt by loosening the tensioning mechanism.
• Remove the old belt carefully.
• Align the new belt with the direction of rotation and place it on the rollers.
• Adjust the tension so that the belt is snug but not overly tight.
• Test the machine briefly to ensure the belt is tracking properly.
How do I maintain my abrasive belt?
• Proper storage: Store belts in a dry, cool place away from direct sunlight and moisture to prevent premature wear or damage.
• Avoid excessive pressure: Apply consistent, moderate pressure during operation to prevent the belt from wearing unevenly or prematurely.
How should I store my abrasive belts?
You should follow these recommendations:
• Climate conditions for storage are preferably 18-22°C and 45-65% relative humidity.
• Avoid exposure to heat sources, direct sunlight or excessive moisture.
• Ensure that product and safety information delivered with the product is available for the end-user.
• Wide belts should be removed from their packaging and stored near to the machine for at least 48 hours before mounting to stabilise to the ambient conditions.
• When unpacked, belts should be hung on a rod or peg not less than 50mm diameter.
How do I know when it’s time to replace the abrasive belt?
Abrasive belts should be replaced when:
• The abrasive material is worn down and no longer provides effective sanding or grinding.
• The belt shows visible signs of damage, such as tears, frays, or deformations.
• The belt’s performance deteriorates, leading to poor surface finish or longer processing times.
How can I extend the lifespan of my abrasive belt?
To extend the lifespan:
• Use proper tension: Ensure that the belt is neither too tight nor too loose on the machine.
• Keep the machine clean: Regularly clean the machine to prevent the buildup of dust and debris, which can wear down the belt faster.
• Avoid overheating: Excessive heat can cause the belt to lose its abrasiveness and degrade faster, so try to avoid working with too much pressure for extended periods.
• Track the belt properly: Make sure the belt runs straight and doesn’t shift off the rollers, which can lead to uneven wear.
Belts General Principles of Safety (F.E.P.A.)
– Abrasive products improperly used can be very dangerous:
• Always follow the instructions provided by the abrasive product and machine supplier,
• Ensure that the abrasive product is suitable for its intended use.
– Be aware of the hazards likely during the use of abrasive belts and observe the recommended precautions to be taken:
• Bodily contact with the abrasive product at operating speed;
• Injury resulting from product breakage during use;
• Grinding debris, sparks and dust generated by the grinding process;
• Noise;
• Vibration.
Never use a machine that is not in good working order or one with defective parts.
– Employers should:
• Carry out a risk assessment on all individual abrasive processes to determine the appropriate protective measures necessary.
• Ensure that their employees are suitably trained to carry out their duties.
Specific Safety Recommendations for the Use of Belts*
• Do not use near flammable materials.
• Abrasive belts can tear. Take precautions against the risk of belt breakage (e.g., protective clothing and devices, machine safety equipment).
• Wear eye protection to shield from flying debris.
• Use ear protection if working with power tools that generate noise.
• Wear a dust mask to avoid inhaling airborne particles.
• Ensure that bystanders are protected from flying chips, sparks, debris, fumes, dust, or noise.
• Belt sanding operations can produce high concentrations of dust, gas, or mist, which can pose a health hazard and an explosion hazard.
• Prevent long hair, ties, loose clothing, or jewelry from coming into contact with the machine and being pulled in. Take precautionary measures.
• Abrasive machines that do not have fully enclosed guards require the operator to wear appropriate personal protective equipment (e.g., protective gloves, fur aprons, face shield, dust mask).
• Check the machine cover locking mechanism. Do not remove the guards. Any contact with the running belts can result in serious injury.
• When assembling, observe the direction of travel marked on the belt.
• After assembling the belt, ensure that the guards are back in place and adjusted correctly. Perform a test run by operating the belt at maximum speed for at least 30 seconds. Check for unusual vibrations or noises and correct them if observed.
• Ensure the workpiece is properly supported and secured to prevent movement.
• Ensure the tool is securely fastened and securely connected to prevent accidents.
• Check the belt for defects or wear before use.
• Belts should only be used dry unless specified as suitable for wet grinding (contact the manufacturer if in doubt).
• Use the center of the belt, if possible, and grind as flat as possible. Avoid grinding with the edge of the belt and avoid damaging the belt with sharp or sharp-edged workpieces.
• Do not apply excessive pressure and avoid overheating the belt.
• Do not open the guard or lower portable machines until the belt has come to a complete stop.
• Check belts in use periodically for wear, tears or damage (e.g., edge cracks, fractures or severe joint wear) and replace them if necessary.
*Adaptation of F.E.P.A. recommendations
Flexible Abrasive Discs
What is a coated abrasive disc?
Coated abrasive discs are used for sanding and finishing surfaces. The flexibility of the backing allows the disc to better adapt to the shape of the surface being worked on, which is useful for working on irregular or curved surfaces.
These discs are often used on machines such as angle grinders or sanders to polish, grind, or remove layers of materials (such as wood, metal, plastic, or paint).
The disc’s flexibility provides greater control and a more uniform finish, especially on surfaces that require a more delicate finish.
What is the difference between coated abrasive discs and grinding discs?
Coated abrasive discs are designed primarily for surface finishing, sanding, and polishing, while grinding discs are intended for more aggressive material removal.
Grinding discs typically have a tougher construction and are used for cutting, grinding, or shaping hard materials.
Coated abrasive discs, on the other hand, are typically used for smoother finishes and are more suited for tasks like sanding and polishing.
What are the best uses for coated abrasive discs?
Coated abrasive discs are used for:
• Metalworking: Grinding, polishing, and deburring metals.
• Woodworking: Sanding and shaping wood.
• Automotive, Nautic & Aerospace: Surface preparation, paint removal, and metal finishing.
• Construction: Sanding concrete, masonry, and stone.
• Plastic and fiberglass: Smoothing and finishing.
How do I choose the right coated abrasive disc?
To select the right coated abrasive disc, consider:
• Material type: The abrasive material (e.g., aluminum oxide for metal, silicon carbide for glass or ceramics).
• Grit size: The finer the grit, the smoother the finish.
• Backing material: Choose based on the application (e.g., paper for light sanding, cloth for heavy grinding).
• Application: The nature of the work (polishing, grinding, or sanding).
What are the fundamental parameters of discs?
The relevant parameters when selecting a disc are:
• Abrasive Type
• Grit
• Surface Finish
• Attachment
• Backing
• Diameter
• Holes
• Work Type (dry/wet)
What are the most commonly used abrasives in discs?
The type of abrasive material used determines the disc’s effectiveness and application.The most common materials are:
• Aluminum oxide (Alox): This is the most widely used abrasive, widely used on wood and ferrous and non-ferrous metals.
• Silicon carbide (SiC): Ideal for harder materials such as glass, ceramics, and stone.
• Zirconium (Zr): Used on hard materials such as stainless steel.
• Ceramic (Cer): For more specific applications on hard metals and wear-resistant materials.
How does grain size affect finish?
The larger the number (grain size), the rougher the finish.
What are the different grades or grits of coated abrasive discs?
There are a wide variety of grits used in coated abrasive discs, depending on the material being worked and the desired result:
• Very coarse grits (16 to 30): for applications involving extensive roughing or material removal.
• Coarse grits (36 to 60): widely used for aggressive material removal.
• Medium grits (80 to 120): used for preparation or intermediate finishing.
• Fine grits (150 to 600): used for smoother, more detailed finishes.
• Very fine grits (800 to 7000): used for specialized work.
What types of grain coatings are there?
Some discs have special coatings to increase efficiency and improve the abrasive’s finish, including:
• Anti-clogging coatings: typically made of stearate, these coatings are designed to reduce abrasive clogging and increase efficiency and life time;
• Cooling coatings, such as Top Size, are designed to prevent the work area from overheating, thus increasing the abrasive’s durability and preventing damage to the workpiece.
How do I attach coated abrasive discs?
Coated abrasive discs can be attached using various methods:
• Hook-and-loop backing: Velcro-style for quick disc changes. This is the most common method.
• Self-adhesive backing: Sticks directly to a sanding pad.
• Center hole: For attachment to a machine spindle or backup pad. This is an uncommon solution.
• Quick-Change: small plastic parts are attached to the disc, usually made of mesh, which screw onto the equipment. This is used only for very small diameters, up to 77 mm.
What are the common backings on discs?
The backing of an abrasive belt is the material that provides the structural support for the abrasive grains, allowing the disc to maintain its shape and strength during use.
The type of backing used in an abrasive disc plays a crucial role in its flexibility, durability, and suitability for different applications.
Backing thickness impacts the disc’s flexibility and durability. Thinner discs are more elastic and suitable for finishing, while thicker discs are more robust and suitable for rough grinding and removing more aggressive material.
Here are the most common types of backings for abrasive discs:
1. Paper Backing
• Description: Paper is, by far, the most commonly used backing. Generally made from a sheet of kraft paper or other paper materials and are often used in light to medium-duty applications.
• Types of Paper Backing: all types of papers are used – from A to F weight – according to flexibility and resistance to wear needs.
• Applications: Fine sanding, finishing, and polishing tasks on wood, metal, and plastic. Normally dry sanding.
2. Cloth Backing
• Description: Cloth backings are made from woven fabrics, typically cotton, polyester or a mix of both. These backings provide strength, and resistance to wear.
• Types of Cloth Backing: Cotton, Polyester and Poly/cotton blends.
• Applications: demanding sanding, normally with coarse grits, in woodworking and metalworking.
3. Film Backing
• Description: Film backings are made from a thin, flexible plastic film (such as polyester or other polymer materials). This type of backing is durable, tear-resistant, and provides a smooth, consistent surface for the abrasive grains.
• Applications: Precision sanding, polishing, and grinding, especially in the automotive, aerospace, and electronics industries.
4. Non-Woven Synthetic Fiber Backing
• Description: Made from synthetic fibers, this type of backing is often used for specialized abrasive products like Scotch-Brite® or non-woven abrasives.
• Aplications: Cleaning, finishing, light sanding, and surface preparation. Offers a softer, more flexible finish compared to other backings. Ideal for tasks that require light abrasive action, like cleaning, polishing, or surface finishing without removing a lot of material.
Each type of backing has specific advantages depending on the type of task you are performing. For heavy-duty applications, cloth and polyester backings are often preferred. For precise finishing work, film and paper backings are typically used.
What are the most common types of additions to abrasive discs?
Adjustments are made to the disc itself to alter the conditions of the base abrasive, giving it, for example, greater cushioning, rigidity, and mechanical or thermal resistance. Additional layers of cloth, sponge, or paper of varying thicknesses are added.
What are the most common diameters of flexible abrasive discs?
The disc diameter depends on the type of base and machine used. Typically, smaller discs are suitable for detail work, while larger discs are used for large surfaces.
Smaller diameters start at around 15 mm, and larger ones can reach 1000 mm. OTA covers this entire range.
The most common dimensions are 75/77, 115, 125, and 150 mm, for use with portable or manual machines, and 250 and 300 mm for stationary machines.
Each diameter can have several holes’ configurations.
What are the most common hole patterns in coated abrasive discs?
The hole pattern is designed to allow for the suction of dust and removed material, improving the cleanliness of the space and the quality of the work.
The disc’s hole pattern should match the pattern of the support base.
Generally speaking, when there is no suction, it is best to use discs without holes.
There are several hole models, usually linked to the disc diameter, as explained in the following table.
Despite the variety of hole models, there are some that fit within them, namely for the most common diameter (150mm): group 1 (6, 7, and 15 holes), group 2 (8, 9, 17, and 49 holes).
There are many other hole patterns, which vary depending on the manufacturer’s options. It is essential that this pattern is consistent with the backing pad and the suction. More complex systems, with more holes, tend to be more demanding in terms of use/placement.
Can I use coated abrasive discs on all surfaces?
Coated abrasive discs can be used on many surfaces, but the abrasive material and grit should match the surface. For example:
• Use Aluminum Oxide (Alox) for metal and wood.
• Silicon carbide (SiC) is ideal for concrete, glass and stone.
• Zirconia (Zr) works well on steel and other hard materials.
• Ceramic (Cer) for inox and other hard metals
Without prejudice to these references, each application must be analyzed, it is common to use, for example, SiC grains in metal or paint, and Zr grains in hard wood.
Posso utilizar o mesmo disco tanto em madeira como em metal?
Yes, but it depends on the type of disc.
For example:
• Wood: Aluminium oxide discs are commonly used for wood, as they offer good cutting action and durability.
• Metal: For metalworking, discs with zirconia or ceramic abrasive are more suitable due to their ability to withstand heat and pressure while providing faster material removal.
While some abrasives can work across multiple materials, it’s best to use an abrasive designed for the specific material to achieve optimal results and prolong its life.
What is the best general purpose abrasive grain?
Aluminium oxide (Alox) is offered in very coarse to very fine grain sizes for a broad array of finishes and general purpose applications.
What’s the difference between “open coat” and “closed coat” abrasives?
Open coat discs have gaps between the abrasive particles, allowing for better heat dissipation and preventing clogging. They are typically used for sanding softer materials like wood.
Closed coat discs have the abrasive particles placed closely together, providing more surface area for aggressive sanding. They are used for harder materials like metal and stone.
Can coated abrasive discs be used for both wet and dry applications?
Yes, coated abrasive discs can be used for both dry and wet sanding, but this depends on the type of disc and the material being worked.
Wet sanding can help reduce heat and dust, extending the life of the disc.
However, not all discs are designed for wet use. There are several paper backings that are not designed for wet use. Cloth or film, on the other hand, typically do not have this drawback.
It is important to check the manufacturer’s recommendations before use.
Can I use coated abrasive discs on a random orbital sander?
Yes, coated abrasive discs with hook-and-loop backing are commonly used on random orbital sanders and can be easily replaced without tools.
Just ensure the disc is the correct size for your sander pad.
Can I use coated abrasive discs on a bench grinder?
Typically, coated abrasive discs are not ideal for use on a bench grinder.
Bench grinders are generally used with grinding wheels.
However, some discs can sometimes be mounted on bench grinders for certain types of material removal.
Check the disc’s specifications before use.
How do I avoid disc slippage during use?
To prevent disc slippage:
• Make sure that the backing pad is proper, clean and free from debris.
• Ensure that the disc is securely attached to the tool (especially for hook-and-loop or adhesive-backed discs).
• Use the correct speed for the disc type and material.
• Check for worn-out or damaged discs and replace them.
How do I know when to replace my coated abrasive disc?
You should replace your coated abrasive disc when:
• The abrasive material has worn down significantly.
• The disc shows signs of damage, such as tears or splits.
• The disc is not effectively removing material or is overheating during use.
• The finish becomes inconsistent or rough.
What are some of the common causes of disc wear and how can I prevent them?
Common causes of disc wear include:
• Overheating: Caused by excessive pressure or speed. Always follow the manufacturer’s guidelines for speed and pressure.
• Clogging: When the abrasive disc fills up with debris, especially when sanding soft materials like wood or paint. Using a disc cleaning stick or choosing a disc designed to resist clogging can help.
• Uneven pressure: Applying uneven pressure can cause the disc to wear out unevenly. Always try to maintain a consistent, light pressure while using the disc.
How can I extend the life of my coated abrasive discs?
To increase the lifespan of your abrasive discs:
• Use them with the proper speed and pressure.
• Keep the disc cool to avoid overheating.
• Change discs when they become worn or clogged.
How do I know the correct speed setting for my power tool when using coated abrasive discs?
The speed setting for your power tool will depend on the type of abrasive disc, the material being worked on, and the specific task.
As a generic rule:
• For coarse-grit discs, use lower speeds to avoid overheating and damaging the material.
• For fine-grit discs, higher speeds are typically used for smoother finishes, but be cautious to avoid burning the material.
Always consult the manufacturer’s guidelines for both the abrasive disc and the power tool for recommended speeds.
Fibre discs
What is a Fiber Disc?
Fiber discs are the most classic of grinding product designs using a heavy-duty coated abrasive disc with resin over resin construction on heavy-duty vulcanized fiber backing.
Ideal for general purpose applications ranging from heavy stock removal to surface blending used with a back-up pad on portable angle grinders.
Vulcanised fibre is a composite material made of cellulose (cotton or cellulose fibres). The name is a reference to the vulcanisation of natural rubber to form hard rubber, which, at a cursory glance, is similar to the production of vulcanised fibre. Vulcanised fibre is made by guiding webs of cotton and/or cellulose fibres through a parchmentising bath containing zinc-chloride solution or sulphuric acid, causing the fibres to partially dissolve. The liquid is subsequently pressed out, which joins the individual fibres and the webs without the addition of any bonding agents.
Thanks to its great mechanical strength and stability at a low weight and outstanding ductility, vulcanised fibre, today, is used also as backing material for abrasive discs, the so-called vulcanised fibre abrasive discs or, in short, fibre discs.
These products are made with backings that have a thickness between 0.4 and 1.0 mm.
Vulcanised fibre is temperature-resistant, but only up to a temperature of 110° C. For this reason, the user should avoid working at pressure levels that exceed recommended levels, as this may cause blistering and burns on the disc, ultimately resulting in grain shedding.
The cellulose used to form the vulcanised fibre backing is hygroscopic, which means it is capable of absorbing and releasing moisture from and into the environment, leading to volume changes in the fibres.
How does a fiber disc differ from a flexible abrasive disc?
The biggest difference is the abrasive backing—fiber vs. paper, film, or cloth—which is much stronger in the former. Therefore, the type of machine they are used on and the attachments are completely different.
Fiber discs are primarily used for grinding, not for final polishing operations.
What are the most common fiber thicknesses in resin fiber discs?
When discussing fiber thickness in resin fiber discs, we’re primarily referring to the thickness of the backing material, which plays a critical role in disc durability, flexibility, and performance.
Resin fiber disc backings typically range from 0.6 mm to 1.0 mm thick:
• Standard-duty (~0.6 – 0.8 mm): more flexible, better for contours or lighter grinding
• Heavy-duty (~0.8 – 1.0 mm): thicker, stiffer backing for more aggressive grinding and durability
These values may vary slightly depending on: the manufacturer, disc diameter and intended application (metal, wood, composite, etc.)
The abrasive grains and grit size affect cutting aggressiveness more than fiber thickness.
Thicker backings are preferred in high-pressure applications, such as weld removal or beveling.
What should I ask when getting information for a resin fiber disc?
The information you need involves the size diameter, size arbor, grain material and grit.
The dimensions are listed as follows: diameter x arbor hole size.
What are common sizes or diameters for a fiber disc?
The most common resin fiber disc sizes are 115mm, 125mm e 180mm.
The diameters 100mm, 150mm e 230 mm are rare and more difficult to find.
What is the typical size and format of a fiber disc arbor?
Resin fiber discs typically have a center hole (arbor). The arbor format is important because it determines how the disc attaches to the backup pad on the angle grinder.
The central hole diameter has 22.23mm (7/8”) and can have the following variants:
• Round hole
• Depressed round hole
• Round hole 4, 8 or 6 slotted
What grains are available in resin fiber discs?
The available grains for a resin fiber disc are aluminium oxide (Alox), zirconia alumina (Zr), silicon carbide (SiC), and ceramic (Cer).
What grits are common for resin fiber discs?
The standard grits for a resin fiber disc run at 16, 24, 36, 40, 50, 60, 80, 100, 120, 150, 180, 220, 240, 280 and 320.
What is the benefit of a resin fiber disc over a flap disc?
A resin fiber disc is more aggressive and designed for faster stock removal, and typically less expensive.
What are common applications for a resin fiber disc?
The most common applications are weld removal, spatter cleaning, beveling, and slag removal.
What grain should be used on different materials?
General purpose falls under either the aluminum oxide or zirconia alumina grains.
Aluminum oxide grains are typically used on aluminum and soft materials.
Silicon carbide resin fiber discs are used for grinding on composite, rubber, or plastic work pieces.
Zirconia or ceramic grains have been proven to be optimal on mild steel.
Ceramic resin fiber discs are optimal on hard and stainless steel.
Does the colour of a fibre disc has a meaning?
Without being a rule, because this depends of the producer marketing decision, the grain types usually have a colour associated:
• The Alox grains normally are brown.
• The ZR grains generally use the blue and sometimes green.
• The SiC are, most of the time, grey or black.
• The Cer grains use red or green.
Are there different types of backing pads for resin fiber discs?
Resin fiber discs can typically be used with two families of backing pads:
• Normal, with flexibiliy soft, medium and hard
• Reinforced, also called turbo, with two configurations: very hard (turbo I) and extra hard (turbo II).
Each backing type helps different types of applications.
• Soft back-up pads are primarily used for lighter applications with finer grits.
• Hard back-up pads are for heavy duty applications, with a recommended grit range of 36-40. Zirconia and Ceramic resin fiber discs are also recommended for hard back-up pads.
• Ceramic grains and coarse grits, like 36 or 40, where pressure is relevant, should normally use turbo backing pads.
What is the rpm rating for resin fiber discs?
The rpm ratings for a resin fiber disc is controlled by the rating on the backing pad.
The standard maximum speed for both (discs and pads) normally is 80m/s, which is translated into 13.300 rpm (Ø115mm), 12.500 rpm (Ø125mm) and 8.500 rpm (Ø180mm).
How is a resin fiber disc held on a angle grinder?
A resin fiber disc is held on a grinder with a back-up pad and center nut.
A spanner wrench is used to take the center nut off and on.
Essential care when storing fiber discs?
Properly storing fiber abrasive discs is essential to ensure their durability, effectiveness, and safety during use. Poor storage can lead to premature wear, deformation, or even accidents.
Here are the recommendations:
1. Store in a dry, ventilated place
-All types of media are very vulnerable to temperature and humidity fluctuations during storage.
-Keep the storage at a constant temperature between 15°C and 27°C.
-Avoid humidity, which can affect the adhesive and warp the disc. Maintain constant humidity levels between 25% and 45%.
-Humid environments can cause the fiber backing to swell and reduce abrasive adhesion. Keep boxes away from damp or cold walls and floors, where they can absorb moisture.
2. Avoid direct exposure to sunlight or heat
-Do not store near heat sources (e.g., heaters, motors). Heat can warp discs and damage abrasives.
3. Original Packaging
-Keep products in their original packaging. In addition to facilitating handling and stacking, discs are typically pressure-packed to prevent warping. Premium discs are packaged in sealed, humidity-controlled bags.
4. Store in a flat, stable location
-Store discs horizontally and stacked evenly.
-Do not fold them or place them under heavy objects to prevent warping.
5. Do not mix types or grits
-Separate by abrasive type and grit size for easier identification and to prevent usage errors.
6. Avoid contact with oils or solvents
-Chemical substances can deteriorate the base material and affect the disc’s effectiveness.
7. Respect the disc’s expiration date
-Some discs have an expiration date; use within this period to ensure performance and safety.
8. Use dedicated supports or cabinets
-Whenever possible, use dedicated supports for abrasive discs or closed cabinets that protect them from dust and physical damage.
Belts General Principles of Safety for Fiber discs
Abrasive products improperly used can be very dangerous:
• Always follow the instructions provided by the abrasive product and machine supplier;
• Ensure that the fiber disc is suitable for its intended use.
Be aware of the hazards likely during the use of fiber discs and observe the recommended precautions to be taken:
• Bodily contact with the abrasive product at operating speed;
• Injury resulting from product breakage or projection during use;
• Grinding debris, sparks and dust generated by the grinding process;
• Noise;
• Vibration.
Never use a machine that is not in good working order or one with defective parts.
Employers should:
• Carry out a risk assessment on all individual abrasive processes to determine the appropriate protective measures necessary;
• Ensure that their employees are suitably trained to carry out their duties.
Safety Instructions for the use of Fiber Discs
• You should take special care if you are not using an angle grinding machine.
• Do not use near flammable materials.
• Always read the safety instructions. Don’t throw away the instructions before reading.
• Examine the disc for damage or unusual stains. Never use a damaged disc.
• Check that the speed marked on the machine is not greater than the speed marked on the disc. Do not use the disc if the speed is lower than the speed marked on the machine, or if no speed is marked on it.
• Never use without a proper back-up pad.
• Align the special nut correctly.
• Ensure the machine guard is fitted.
• Ensure work piece is secure.
• Never grind without protective equipment.
• Wear gloves and eye protection to shield from flying debris.
• Use ear protection if working with tools that generate noise.
• Wear a dust mask to avoid inhaling airborne particles.
• Ensure that bystanders are protected from flying chips, sparks, debris, fumes, dust, or noise.
• After assembling the fiber disc, ensure that the guards are back in place and adjusted correctly. Perform a test run by operating the disc at maximum speed. Check for unusual vibrations or noises and correct them if observed.
• Fiber discs should only be used dry unless specified as suitable for wet grinding (contact the manufacturer if in doubt).
• Only use for grinding – 10º angle. Do not use for cutting.
• Work from side to side without excessive force. Never force on the disc.
• Check discs in use periodically for wear, tears or damage (e.g., edge cracks, fractures or severe wear) and replace them if necessary.
Flap discs
What are flap discs?
Flap discs consist of small, overlapping sheets of abrasive material (flaps), fixed to a base.
They are designed for right-angle or near-right-angle grinding applications, for applications ranging from high stock removal to medium finishing.
Because a flap disc has multiple layers, new grit is exposed on each flap as the others wear down.
What are the advantages of flap discs?
Some of the benefits of flap discs are:
– Excellent versatility: flap discs allow for sanding and finishing with a single tool. They are ideal for applications ranging from carpentry to concrete grinding or finishing.
– Greater maneuverability: A flap disc is a lightweight and easy-to-use solution, allowing grinders to complete tasks quickly and accurately.
– Reduced noise and vibration: Worker safety and comfort are essential in environments requiring abrasive materials. Abrasive flap discs are quieter and vibrate less, making them safer and more comfortable for your team.
– Longer life: flap discs require fewer replacements over time and remain functional for a long time. This durability results in lower costs in the long run.
What are the types of flap discs?
In terms of shape, there are two types of discs: Type 27 (flat), which have a flat face, and Type 29 (conic), which have an angled face. These are the most common.
• Flat Discs (Type 27):
Flat flap discs typically grind best at smaller angles, between 0 and 15 degrees. They are ideal for smooth finishing on flat surfaces and can handle light contours.
• Conic Discs (Type 29):
Conic flap discs have a dish-shaped grinding surface rather than a flat one. They work best at angles between 15 and 35 degrees. They allow for aggressive material removal.
In general, conic flap discs are used for initial grinding, which requires a more aggressive action, and flat discs for final finishing or precision refinement.
What are the most common types of abrasives in flap discs?
The most common abrasives in flap discs are: zirconium, ceramic, and aluminium oxide, in that order.
• Zirconium (Zr) is a blend of zirconia and aluminum grains with self-sharpening capabilities. It is tough, durable, and heat-resistant, making it the ideal choice for applications on low-carbon and carbon steel. This option is perfect for aggressive stock removal and grinding. It provides fast cutting and excellent longevity.
• Ceramic (Cer): Ceramic discs offer superior performance and are especially effective on stainless and high-alloy steels. As they wear, the grains micro-fracture to expose consistently fresh, sharp edges. It provides faster cuts and maximizes grain utilization, offering long-lasting durability.
• Aluminum oxide (Alox): This is typically the most economical solution and can offer a good quality-price ratio. They are less common.
What materials are flap discs used on?
As a general rule, each grit type is associated with a specific material being worked, such as:
• Ceramic discs are used on stainless steel or very hard steel.
• Zirconium or aluminum oxide discs are typically used on aluminum.
• Zirconium or ceramic discs are proven to be ideal for carbon steels.
Selecting the Appropriate Grit
Flap discs are produced in various grit sizes.
Abrasives with lower grit numbers are an excellent starting point for stock removal and standard grinding. Abrasives with higher grit numbers (and therefore finer grits) provide a smoother finish.
The choice depends on the project stage and the desired result, following some basic guidelines:
• Grits 36 and 40: These grits are the most abrasive and facilitate heavy-duty operations, such as stock removal.
• Grits between 40 and 60: Any of these abrasive grits can be used for weld grinding and deburring.
• Grits 60 and 80: As the abrasive grit gets finer, it is best suited for rust removal applications.
• Grits between 80 and 120: The finest abrasive grit in this range is ideal for fine-tuning applications such as cleaning and finishing.
Stainless steel, for example, generally requires additional surface finishing processes due to the properties that each one confers on the material.
How do I identify the disc’s grain type?
There are no universal solutions but:
• Blue grains are usually Zirconium;
• Bright red grains are typically Ceramic;
• Brownish grains are usually Aluminum Oxide.
What are the typical dimensions of a flap disc?
Flap discs have two basic dimensions: the outer diameter and the central hole diameter. The thickness depends on the arrangement of the flaps and the type of support, and is not clearly stated.
The most common diameters of flap discs are: 100, 115, 125, 150, and 180 mm.
A 22 mm (7/8″) central hole is almost universal, and smaller discs can also have a 16 mm (5/8″) diameter.
What are the most common backing for flap discs?
The backing provides stability during use, and the most commonly used solutions are fiberglass, plastic/nylon, and, more rarely, aluminium.
• Fiberglass backing – It is robust, lightweight, and secure, forming a solid bond with the adhesives and eliminating the possibility of contamination of the work surface. It absorbs vibrations well, making it excellent for operator comfort. Because fiberglass is layered, the rigidity required for the backing is easily adjusted. These backings are the most common.
• Plastic backing – Plastic backings are becoming more popular because they are more economical and comfortable to use. Various types of plastic are used, although nylon is the most common.
• Aluminium backing – Aluminium backings are the least popular, but they are excellent for applications requiring very high strength and rigidity, particularly for heavier grinding. They are typically the most expensive backings and are relatively rare.
What are the most common applications for flap discs?
Flap discs can be used for:
• Removing solder and other material in metal fabrication
• Deburring
• Finishing metal surfaces
• Grinding and finishing all types of metals
• Removing paint and rust
• Smoothing and shaping wood
• Polishing concrete
• Shining and polishing
What machines are flap discs used on?
Flap discs are used on straight-angle grinders.
Flap discs can be used on a lower-powered tool, but these products are designed for high-powered tools.
What is the advantage of a flap disc over a resin-bonded fiber disc?
A flap disc is more durable than a fiber disc and can leave a finer finish, but it is typically more expensive.
What are the advantages of flap discs vs. bonded grinding discs?
Flap discs have the following advantages over bonded abrasive grinding discs:
• Less pressure required to achieve results;
• More flexible, which provides less vibration and noise than a grinding disc;
• More controlled material removal;
• Lower grinding temperatures;
• Cost-effective;
• Lightweight and easy to maneuver;
• Better finish and fewer scratches than other discs;
• Excellent contact with the work surface.
What does HD mean on a flap disc?
HD stands for heavy duty – high density, which means it has more flaps than a standard flap disc, meaning it lasts longer and can be less aggressive.
What is the essential information when ordering a flap disc?
The following information is essential:
• Diameter
• Type/shape: conical (29) or flat (27)
• Abrasive type: Zr, Cer, or Alox
• Grit: typically 36 to 120
Belts General Principles of Safety for Flap Discs
Abrasive products improperly used can be very dangerous:
• Always follow the instructions provided by the abrasive product and machine supplier,
• Ensure that the flap disc is suitable for its intended use.
Be aware of the hazards likely during the use of flap discs and observe the recommended precautions to be taken:
• Bodily contact with the abrasive product at operating speed,
• Injury resulting from product breakage or projection during use,
• Grinding debris, sparks and dust generated by the grinding process,
• Noise,
• Vibration.
Never use a machine that is not in good working order or one with defective parts.
Employers should:
• Carry out a risk assessment on all individual abrasive processes to determine the appropriate protective measures necessary.
• Ensure that their employees are suitably trained to carry out their duties.
Safety Instructions for the use of Flap Discs
• You should take special care if you are not using an angle grinding machine.
• Do not use near flammable materials.
• Always read the safety instructions. Don’t throw away the instructions before reading.
• Examine the disc for damage or unusual stains. Never use a damaged disc.
• Check that the speed marked on the machine is not greater than the speed marked on the disc. Do not use the disc if the speed is lower than the speed marked on the machine, or if no speed is marked on it.
• Align flanges correctly.
• Ensure the machine guard is fitted.
• Ensure work piece is secure.
• Never grind without protective equipment.
• Wear gloves and eye protection to shield from flying debris.
• Use ear protection if working with tools that generate noise.
• Wear a dust mask to avoid inhaling airborne particles.
• Ensure that bystanders are protected from flying chips, sparks, debris, fumes, dust, or noise.
• After assembling the flap disc, ensure that the guards are back in place and adjusted correctly. Perform a test run by operating the disc at maximum speed. Check for unusual vibrations or noises and correct them if observed.
• Flap discs should only be used dry unless specified as suitable for wet grinding (contact the manufacturer if in doubt).
• Only use for grinding. Do not use for cutting.
• Work from side to side without excessive force. Never force on the disc.
• Check discs in use periodically for wear, tears or damage (e.g., edge cracks, fractures or severe wear) and replace them if necessary.
GENERAL PRINCIPLES OF SAFETY (FEPA)
Every effort has been made to ensure that all information supplied is accurate and up to date.
We cannot accept, however, responsibility for any error or omission, nor for any consequential loss or damage so arising.
Abrasive products improperly used can be very dangerous:
• Always follow the instructions provided by the abrasive product and machine supplier.
• Ensure that the abrasive product is suitable for its intended use.
• Examine all abrasive products for damage or defects before mounting.
• Follow the correct procedures for handling and storage of abrasive products.
Be aware of the hazards likely during the use of abrasive products and observe the recommended precautions to be taken:
• Bodily contact with the abrasive product at operating speed
• Injury resulting from product breakage during use
• Grinding debris, sparks, fumes and dust generated by the grinding process
• Noise
• Vibration
Use only abrasive products conforming to the highest standards of safety. The following EN standards provide the essential safety requirements for relevant abrasives products:
• EN 12413 for Bonded Abrasives
• EN 13236 for Superabrasives
• EN 13743 for Specific Coated Abrasives (vulcanised fibre discs, flap wheels, flap discs and spindle-mounted flap wheels).
Never use a machine that is not in good working order or one with defective parts.
Employers should carry out a risk assessment on all individual abrasive processes to determine the appropriate protective measures necessary. They should ensure that their employees are suitably trained to carry out their duties.
PRECAUTIONS AGAINST LIKELY HAZARDS
Bodily contact with the abrasive product:
-Always take great care and attention when using abrasive products. Tie back long hair and do not wear loose clothing, ties and jewellery.
-Prevent accidental start-up of the machine before mounting or changing an abrasive product. Isolate machines from their power source where necessary.
-Never remove guards from machines where fitted and ensure they are in good condition and properly adjusted before starting the machine.
-Always use gloves and suitable clothing where the workpiece or machine is hand-held.
-For gloves, a minimum protection level of EN 388 Category 2 is recommended.
-After switching off the machine, ensure the product has come to rest before leaving the machine unattended.
Injury caused by product breakage:
-Always handle abrasives with great care, they are easily damaged. Examine all products for defects or damage before use.
-Store abrasives in dry, frost-free conditions avoiding wide variations in temperature. Ensure they are properly protected and supported to prevent damage and distortion.
-Coated abrasives should be stored at 18-22º C, 45-65% relative humidity.
-Abrasive belts should be hung on a rod or peg not less than 50mm diameter.
-Never use an abrasive product beyond its expiry date where marked. Observe the recommended shelf life for the following specific products: Resinoid and Shellac products 3 years; Rubber products 5 years; Vitrified products 10 years.
-Check abrasive product or package for any warnings or other safety information.
-Ensure that the correct abrasive product is selected. Never use a product if it cannot be properly identified.
-Follow the instructions provided by the abrasive product or machine supplier when mounting abrasive products. Observe any mounting indications marked on the product such as direction of run or mounting position.
-Never force the abrasive product onto the mounting fixture or modify it to fit.
-Never exceed the maximum operating speed where specified.
-Check that the correct mounting devices are used and that they are undistorted, clean and free from burrs.
-Do not tighten the mounting device excessively.
-After mounting or re-mounting an abrasive product, conduct a trial run at operating speed with the guard in place for at least 30 seconds, standing clear of the machine before use.
-Never remove guards from machines where fitted and ensure they are in good condition and properly adjusted.
-Ensure that the workpiece is secure and properly supported. Ensure that work rests are properly adjusted and secure.
-Never start the machine with the workpiece in contact with the abrasive product.
-Never apply excessive force or shock to the abrasive product or let it overheat.
-Do not grind on the part of the product that is not designed for the operation. Avoid grinding with the edge of abrasive belts, use the centre of the belt if possible.
-Avoid clogging and uneven wear to ensure that the abrasive product is working efficiently.
-Let the abrasive product stop naturally, not by applying pressure to its surface.
-Turn off and spin out excess coolant before stopping the machine.
-Do not leave abrasive belts under tension when not in use.
Grinding debris – sparks, dust and fumes:
-Exposure to grinding debris can cause lung damage and other physical injuries.
-All dry grinding processes should be provided with adequate extraction facilities.
-Do not use abrasive products near flammable materials.
-The use of respirators complying with EN149 is recommended for dry grinding processes even if extraction systems are provided.
-Guards where provided should be adjusted to deflect sparks and debris away from the operator.
-Take additional measures to protect people working nearby.
-Eye protection is recommended for all machine applications for abrasives. For handheld machines or workpiece, goggles or full-face shields with a minimum protection level of EN166 Grade B are recommended.
-Ensure that the correct abrasive product is selected. An unsuitable product can produce excessive debris and dust.
PRECAUTIONS AGAINST LIKELY HAZARDS
Noise:
-Ear protection complying with EN352 is recommended for all applications where the workpiece or machine is hand-held, irrespective of the noise level.
-Ensure that the correct abrasive product is selected. An unsuitable product can produce excessive noise.
Vibration:
-Processes where the workpiece or machine is hand-held can cause vibration injury.
-Action needs to be taken if tingling, pins and needles or numbness is experienced after 10 minutes continuous use of the abrasive product.
-The effects of vibration are more pronounced in cold conditions so keep the hands warm and exercise hands and fingers regularly. Use modern equipment with low vibration levels.
-Maintain all equipment in good condition and stop the machine and have it checked if excessive vibration occurs.
-Use good quality abrasive products and keep them in good condition during their life.
-Maintain mounting flanges and back-up pads in good condition and replace if worn or distorted.
-Do not grip the workpiece or machine too tightly and do not exert excessive pressure on the abrasive product.
-Avoid continuous use of the abrasive product.
-Use the correct product. An unsuitable product can produce excessive vibration.
-Don’t ignore the physical symptoms of vibration – seek medical advice.
DISPOSAL OF ABRASIVES
• Used or defective abrasives should be disposed in accordance with local or national regulations.
• Further information can be obtained from Voluntary Product Information provided by the supplier.
• Be aware that the abrasive product may be contaminated with material from the workpiece or process after use.
• Disposed abrasive products should be damaged to prevent them from being taken from waste skips and re-used.
