Shopping for a grinding belt, the first concern is usually the type of abrasive grain and size Open coat aluminium oxide is great for finishing wood. On the other hand, ceramic provides unparalleled performance when working with steel when knife making and fabricating.
Another important aspect to the application is the backing material and its thickness, both of which will vary depending on the process you’re utilizing. Choosing the right backing and thickness means a long working life and superior results while the wrong one could lead to premature tearing, workpiece scorching, and more.
Various belt grinders operate with different diameter contact wheels and some contact wheels can only be used with lighter more flexible backings as the have the ability to confirm to the small radius of some wheels.
Belt Thickness Weights
With abrasives, backing thickness is categorized by the alphabet, with those having an A rating being the most flexible and Y weight backings being the sturdiest.
Here are some general guidelines:
Cloth – Cloth backings come in various weights, from Stiffest to the most Flexible – (Y, X, J, F)
“Y” Weight – This extremely heavy duty cloth is used for tough applications. It is usually made of Polyester for added strength & tear resistance.
“X” Weight – This heavy cloth, also called drills, is recommended for all ordinary machine sanding operations.
“J” Weight – This flexible, lightweight cloth, also called jeans, is used where more flexibility is needed, such as with contour sanding.
“F” Weight – This highly flexible, lightweight jeans cloth is used when extreme flexibility is desired.
Paper – Paper backings come in different paper weights, designated by letters, are available for different applications.
“A” Weight – This light touch 40# paper is primarily used in finishing operations where fine grits are required.
“C” Weight – This medium light 70# paper is used when some pliability and strength are required. It can be used in folded or flat areas and is ideal for cabinetwork. This backing is available in fine to medium grits.
“D” Weight – This medium heavy 90# paper is available in medium and coarse grits.
“E” Weight – This strong 130# paper is used for belts, discs, rolls and very coarse sheets.
“F” Weight – This 165# paper is used for narrow and wide belts, metal and crankshaft polishing rolls, and cabinet and furniture industries.
A, B,C, D, E, and F weights are all made from paper of varying durability.
A and B weight materials are primarily used for hand-sanding applications, making them appropriate for fine wood finishing.
C and D weights are seen on general use sanding products as opposed to those designed for speciality applications. They are chosen for hand-sanding as well as use on smaller portable power sanders.
E and F-weights are often used to make sanding rolls, sanding belts and sanding discs for applications that call for high resistance to tearing, as they are the strongest paper backings.
X' and Y-weight backings are typically used in metalworking. X-weights tend to be made from a cloth material that is stiff but supports greater flexibility while Y-weights are fully or partially synthetic and used for heavy-duty applications.
Other weights, like S, T, M, and H, are used only for specific applications and products. For example, H-weight is the strongest cloth backing and used exclusively with zirconia.
J-weight belts use a highly flexible cloth backing material. The ‘J’ categorization comes from the fact that they are similar in weight to a pair of jeans, so they’re durable while remaining pliable enough to contour rounder surfaces like knife handles and crankshafts.
These belts are used primarily for applications where heavy stock removal isn’t necessary and where you want the belt surface to conform to the surface you are sanding, grinding or polishing. A perfect example is crankshaft polishing. With the various radii and curved surfaces that must be polished on a crankshaft, a highly flexible but durable belt is necessary and J-weight belts fit the bill perfectly.
Ideal abrasive performance calls for the right ratio of flatness, weight, and flexibility. J-weight backing material is light and flexible, making it popular in applications where the abrasive surface needs to conform to a curved workpiece surface.
J-weight belts are typically used when slack grinding, without a platen or contact wheel, so they can apply a uniform finish to curved surfaces. An important thing to note about J-weight belts is that the joint can “bump” the workpiece if it’s used against a flat platen. This is why it’s important to use them only when slack grinding or with a rotary platen attachment.
Their versatility makes them an ideal choice for metalworking applications like welding touch-ups, blacksmith work, and knifemaking, but they also do a great job on wood, plastics, composites, and painted surfaces.
Materials used to cut
Natural; Emery, Garnet
Synthetic; Aluminium Oxide, Silicon Carbide, Alumina-Zirconia, Ceramic Aluminium Oxide, Diamonds
Emery is dull black in colour. It is hard, round and blocky in structure.
Garnet is a reddish brown in colour. It is of medium hardness with good cutting edges and has the tendency to break or refracture when in use, thus creating new cutting edges.
Aluminium Oxide is a brown coloured mineral that is tough and durable and the most widely used abrasive grain. It is coated in the entire grade range and is most commonly used in the metal, wood, leather and shoe industries.
Silicon Carbide is a shiny black, sharp, very hard mineral that is coated in the entire grade range. It is used for a wide range of non-ferrous metals such as brass, titanium, the finishing of stainless steel, shoe trades, extensively for sanding primer, sealer, and top coats of paint and clear finishes. It is also the most effective grain for removing primary metal scale.
Alumina-Zirconia is an alloy mineral of aluminium and zirconium oxide that is very effective for coarse grade stock removal of metal and wood.
Diamonds are extremely hard and used to cut ceramics, stone, and very hard metal alloys such as tungsten carbide. Because of high cost, usage is limited to material that cannot be cut with other abrasives.
Ceramic Aluminium Oxide is a mineral that is neither sintered nor fused. Compared to conventional aluminium oxide, this white mineral is two to three times tougher.