This article originally appeared in the August print issue of IMPO.
Most every manufacturing facility has a countless inventory of abrasives in a variety of grains for different applications and finishes. The challenge for many is aligning the results needed with the materials available, and thus selection options — and concerns — can be enough to make the average manufacturing worker’s head spin.
Selection Based on Metal
“Each type of metal has its own set of properties and different abrasive grains will create different results,” explains Kate Ouellette, Marketing Manager for Rex Cut Abrasives. For the majority of applications, Rex Cut suggest aluminum oxide due to its versatility. For applications requiring higher purity or brighter surface finish, such as medical implants or select aerospace components, silicon carbide might be preferable due to its sharper grain. When it comes to the most common types of metal being used, the experts have some suggestions:
Aluminum: Aluminum isn’t the easiest of metals to grind due to its low melting temperature. As you grind and heat up the metal, it tends to gum up your wheel. Says Ouellette, “To work on this metal without using waxes or compounds, try an abrasive product that is naturally non-loading, such as Type 27 Max Flex or any of Rex-Cut’s cotton-fiber based products.”
Steel: “When grinding on regular steel applications, brown aluminum oxide grain abrasives work best for general purpose uses and are less costly than Zirconia,” says Dean Daniel of Shark Industries, Ltd., a supplier of small cut-off wheels. “You require a Zirconia grain based product for grinding heavier metals or stainless steel products. For longer life on harder metals and stainless steel, you should use the Zirconia or Ceramic grains with a larger percentage of either grain in the product for best results. They will give you less bluing from heat build-up on your stainless steel applications.”
It’s also important to note how much metal needs to be removed when selecting a grit size. For example, deburring a cast part and removing a weld are not equal jobs. “The lower the grit number, the coarser the grain,” explains Ouellette. “For faster stock removal, select a coarse grit. For light deburring, edge-breaking, blending, or as a second step to achieve a better surface finish, a finer grit will do the trick.”
A Strong Finish
Does your application require a satin finish, a food grade finish, or does the finish even matter? This is a very important factor in selecting the right abrasive product. If you just need to remove a weld quickly and surface finish isn’t important, a typical coarse grinding wheel will work. “If finish is a priority, we have a few suggestions for you,” says Ouellette.
- Sigma Green Grinding Wheel (type 27) is designed to remove a weld fast and leave a 100 RA finish, especially on 304 stainless steel.
- Type 27 Max Flex, which excels on aluminum, is flexible and provides a wider surface contact area while working, giving you a uniform finish. This wheel is often used as a second step after Sigma Green.
- Fusion Interleaf Flap Disc allows you to achieve a #4 finish in almost no time at all. Fusion is made up of multiple layers of premium coated abrasive cloth and non-woven surface conditioning material. This combination allows for quick, controlled light grinding and an even finish.
- Rex-Cut Type 1 wheels are designed for controlled metal removal without changing part geometry. These wheels leave a superior surface finish and are often used in automotive, aircraft/aerospace, tool & die, as well as oil field repair/maintenance.
- Rex-Cut Mounted Points, which are made of the same material as our type 1 wheels, are capable of leaving a 32 RMS surface finish on stainless steel and titanium. Effective for final finishing, these mounted points come in numerous shapes.
Ouellette also adds that it’s important to consider the workspace accessibility since often welds, burrs and sharp edges are in hard-to-reach areas. To reach inside corner welds, Rex-Cut has a unitized inside corner blending disc available. For applications in even smaller areas, such as deburring an i.d., mounted points are a great option. A, B, and W shapes are available in cotton fiber, unitized and rubber. For even smaller areas where grinders can’t reach, handheld finishing sticks are an option.