Abrasives that make the grade

Selecting and using abrasive products correctly

PRACTICAL WELDING TODAY® MAY/JUNE 2005

May 10, 2005

By:

Efficient and economical metalworking, from cut-off and grinding operations to blending welds to final finishing, depends on selecting abrasives of the right kind and grade and using them safely.

Metalworking Abrasives

Professional metalworkers hardly need reminding that maximizing output and minimizing costs in welding require selecting the right abrasive for each application and using that abrasive correctly.

Still, in the rush to get the job done or the finished product out the door, too often many use whatever abrasive is handy, fail to match the abrasive product to the machine, or ignore fundamental grinding safety rules. The results can be lower-quality products, increased grinding or finishing costs, and lost productivity.

Selecting Abrasives by Grade: Good, Better, Best

Those who measure total grinding results and want to achieve the lowest grinding cost for an application will consider the bestabrasive products available and reserve the use of betterabrasives for high-productivity applications in which initial abrasive costs are important. Fabricators who want the lowest initial abrasive costs likely will select good abrasives, but should understand that such a choice may not be as economical in the long run.

If you do not measure total grinding results but want to, you can work with your abrasive supplier to test various grades of abrasives or abrasives products from different manufacturers. Such tests, performed in your shop, can determine relative abrasive cost based on initial cost and wear rate and measure relative worker productivity based on a worker's wages. Then, relative wheel cost can be added to the operator's cost to determine the total grinding cost. What such tests typically show is that the most advanced (best) abrasive product typically lasts longer, works faster and may be the most cost-effective choice.

Abrasive Selection Guide
Figure 1
Click to see the Abrasives Selection Guide. These abrasive selection guidelines are for typical welding and metal fabrication operations. Products are listed in descending order: 1 = best, 2 = better, and 3 = good for the applications listed.

Using Abrasives Safely

One of the most fundamental rules for using grinding products safely is to match the abrasive product to the machine being used. Abrasives manufacturers' catalogs clearly specify which products are designed for which machines. Some use icons or other graphical representations of allowable machine/abrasive matches. Operators also should look for similar information on product packaging. In fact, the No. 1 safety rule for all abrasive disks and wheels is to read and follow the safety information included on the product packaging. If the packaging has been discarded, make sure you know what you have mounted onto a machine and follow appropriate safety procedures.

The following are tips for properly using and maintaining abrasive products.

General:

  • Do not grind near flammable materials.
  • If possible, grind or sand in a well-ventilated area.
  • Wear eye and face protection.
  • Wear safety gloves.
  • Hold the grinder with both hands.
  • Direct sparks away from your body and away from bystanders.
  • Do not wear loose-fitting clothing.
  • Wear long-sleeved shirts or arm guards and long pants.
  • Do not wear polyester-type clothing when grinding. Polyester is a byproduct of petroleum and is flammable.
  • When necessary, use a dust mask or approved respiratory protection appropriate for materials being abraded or ground.
  • Wear hearing protection when noise exposure exceeds established threshold levels.
  • If chatter or vibration occurs during grinding, stop the tool at once. Determine the cause of the problem and correct it before continuing.
  • Rotate stock; use it on a first-in, first-out basis.
  • Do not grind soft metals on large grit-size grinding wheels. The soft metal can build up in the wheel, possibly causing it to break or causing the soft metal to "fly" off the wheel. Use silicon carbide wheels for nonsteel applications such as grinding carbides, cast iron, and all nonferrous metals. Use aluminum oxide for steel applications such as carbon steel, iron forgings, stainless steel, and other alloys.

Grinding wheels:

  • Store wheels in a dry environment.
  • Do not subject wheels to dramatic temperature changes or near-freezing temperatures.
  • Do not mount a cracked, dropped, chipped, or otherwise damaged wheel.
  • Ensure that guards and work rests are adjusted and secure.
  • Use safety guards that cover at least half the wheel.
  • Run a newly mounted wheel for one minute or more before grinding with it. During this test, do not stand in front of or in line with the wheel.
  • Be sure that flanges are clean, flat, and free of burrs.
  • Do not overtighten flange retaining nuts.
  • Check machine speed against the safe maximum operating speed specified on the grinding wheel. Never use a grinding wheel with a rated speed less than that of the grinder, and never exceed the maximum operating speed of a grinding wheel.
  • Special warning: Never use a high-speed air sander with a grinding wheel as a portable grinder. Recently many tragic injuries have resulted from the use of high-speed, pistol-grip air sanders mounted with grinding wheels. Because the speed of these air sanders far exceeds the maximum rated speeds for grinding wheels, a potentially lethal wheel breakage may occur. With these machines, use only sanding disks specifically designed for air sanders.

Fiber disks:

  • Store abrasive disks at 40 percent to 50 percent relative humidity and 60 to 80 degrees F.
  • Store coated abrasive disks at least 4 inches above the surface of concrete floors, away from open windows, out of direct sunlight, and away from heat sources.
  • Store coated abrasive disks in their original packaging.
  • If packaging is received damaged, don't use the product inside. Return any damaged product to its manufacturer.
  • Never use a coated abrasive disk with nicks, cuts, tears, or any other visible damage.
  • Use only a disk that fully contacts the backup pad. Never use a warped disk.
  • Start a tool just off the workpiece and bring it up to full operating speed before beginning grinding or sanding.
  • Always ease the fiber disk into the workpiece at a 5- to 10-degree angle to the workpiece surface.
  • Never alter the size or shape of an abrasive disk or its backup pad.
  • If you're using a see-through disk (with scooped holes), don't start the equipment before ensuring that no object is protruding through one of the holes.

Even if you're using the right abrasive product to get the job done, remember how important it is to use grinding and sanding equipment as though your life depended on it. Only then can you ensure the greatest productivity, cost savings, and safety.

Jim Elving is coated abrasives product manager at Saint-Gobain Abrasives, One New Bond St., P.O. Box 15008, Worcester, MA 01615-0008, 508-795-5000, www.nortonabrasives.com.



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