Guide to Understanding Abrasive Wheels

Whether you are cutting off a frozen bolt, prepping for a weld, or you want to create a beautiful brushed pattern on stainless steel sheet, abrasive wheels are an essential tool for any welder or metal fabricator. IMS stocks a huge selection of abrasive metal wheels in all sizes, styles and varieties for cutting, grinding and finishing metal.

Abrasive wheels are similar to sandpaper. They are made from powdered abrasive grains held together with a binder, such as resin, which also glues them to a fiberglass backing in the shape of a wheel. As the wheel rotates on a grinder it abrades the metal surface, causing sharp edges of the grains to either break off, leaving more sharp edges, or wear down. Gradually the worn grains are pulled out of the binder, exposing sharper grains in place behind them.

This guide will help you select the right abrasive wheel, including the best choice of grain type and size, as well as binder material, for your application.

The four primary types of grains used on abrasive wheels for metal include aluminum oxide, zirconia alumina, silicon carbide, and ceramic alumina:

• Aluminum oxide grains are tough and hard-wearing, making this type of abrasive wheel a good choice for grinding metals such as steel, stainless steel and other ferrous metals.


• Zirconia alumina grains also can be used to grind steel and steel alloys. It costs more but lasts longer than aluminum oxide. Zirconia is very heat resistant and is typically used for high pressure machining and grinding because the pressure causes the grains to break down quickly, exposing sharper edges.


• Silicon carbide grains are very sharp, but break off easily under high pressure. They can be used for grinding softer or weaker metals, such as copper or cast iron, or non-metals such as cement or sto


• Ceramic alumina is a newer type of abrasive with a micro-grain structure that breaks down in smaller pieces, giving it a longer life and fast cut rate. This type of abrasive works well in a range of applications, from cast aluminum to titanium alloys.

The different types of grains can also be blended, to create an optimal formula for specific metals and applications.

 

Grit size, which reflects the size of the grains, is denoted on the wheel label. The larger the grit size, the smaller the grain. As with sandpaper, large or coarse grains take out larger chips from the metal, resulting in a rougher finish. The smaller the grain, the finer the finish. Also, larger grains are more appropriate for softer materials, such as low-carbon steel, while smaller grains should be used on harder alloys.

Binder materials are graded by their ability to hold the grains. The stronger the binder, the longer the grains hold on, even though they have been dulled. This means that a weaker binder is a better choice for cutting strong, tough metals that require razor sharp abrasive grains. Many abrasive wheels used for standard metalworking use a resin binder.

IMS stocks a varied line of abrasives including:

• Metal cutting wheels – used with an angle grinder to make fast, clean cuts in steel, stainless steel and other metals.


• Sanding discs – remove paint, rust, corrosion, surface marks and uneven edges to create a smooth finish.


• Bench grinding wheels – use with a bench or pedestal grinder to remove metal, shape, sharpen or deburr.


• Flap discs – a flat, circular abrasive disk made of multiple overlapping cloth-backed “flaps” joined at the center. Used with a grinding wheel to blend or finish a welded surface and prepare it for priming or painting.


• Flap wheels – similar to a flap disk, but the flaps are arranged around a central hub in a three-dimensional tire shape. Used to create a smooth finish on curved metal.


• Wire wheels – prepare welding surfaces by cleaning off spatter and excess filler material without removing base metal.


• Shank mounted points – rotating abrasive points in a variety of shapes and materials allow fast, free-cutting stock removal, blending and polishing.


• Carbide burrs – used with a grinder or in a CNC machine, these tungsten carbide rotary files with raised diagonal teeth are used for cutting, shaping, grinding and deburring.