Safety Requirements for Using Abrasive Cup Wheels

Doing it right the first time is always the best and cheapest way, and using abrasive cup wheels is no different. Abrasive cup wheels are a fast, convenient way of grinding and cutting, but like any cutting tool, you must use caution and plan ahead. By following OSHA and ANSI safety standards, you can be sure you are doing the job the right way and preventing costly accidents. The investment you make early on to learn and apply basic safety precautions definitely pays off in a safer work environment later on. Here's a list covering what you should know about using an abrasive cup grinder:


Match the Wheel to the Machine

You don't drive nails with a screwdriver any more than you would set screws with a hammer, but that's roughly what you're doing if you try to use a cup grinder on the wrong rotary tool. Always check the manufacturer's recommendations for compatible machinery and take the instructions to heart; a poorly fitted wheel is just waiting to hop off at the worst time and cause some real harm.

Make sure the cup is firmly attached to the proper mounting point on the rotary tool. Run the machine for a few seconds at low speed to check for alignment and balance problems. If the cup seems to wobble, even a little, take it off and try again.

Toolroom Cup Grinding - Personal Protection Equipment


Cup Wheel Speed vs. Machine Speed

Every cup wheel has a maximum rated speed that was worked out by engineers under laboratory conditions. When the label tells you that this cup grinder is rated for X revolutions per minute, that's information you can trust. Only mount your grinder to a machine with a speed no greater than the wheel's maximum operating speed. That way, you – and your less-experienced shop workers – will never accidentally apply a speed greater than what your wheel can safely handle.

Apart from the following the wheel’s maximum speed, you need to make sure your grinding machine has a proper back flange and guard. A proper guard extends far enough to keep debris and sparks away from your fingers and hands (see photo above). A proper back flange is flat across the entire contact surface in order to provide support for the cup. Its diameter is also at least one-third that of the wheel. ANSI B7.1 calls for back flange sizes as follows:

Snagging Cup Wheel

Cup Diameter

   Minimum Back-Flange Diameter                         

6 inches

5 inches

4 inches

   2 inches

   1-3/4 inch

   1-3/8 inch

Cup Wheel Mounting Checklist

Did you know that jet pilots have a checklist they follow before every flight? No matter how experienced you are or how many times you've done it, you can always have a bad morning and miss one or two important details. Like the pilot, you can use a checklist when you're mounting the wheel to make sure you've gotten it right. . . even if it's the hundredth time you've done this:

  • Check your wheel storage area to be sure the wheel has been properly stored in its original package, on a shelf, and away from moisture and temperature extremes.

  • Visually inspect all of the abrasive cup wheels you plan to use, as well as their packaging for damage. Never use a damaged abrasive cup wheel.

  • Disconnect the machine from its power source before beginning to mount or dismount an abrasive cup wheel.

  • Inspect the machine and its wheel guard. Never use a damaged machine or guard.

  • Inspect and clean the machine’s back flange and mounting threads.

  • When mounting or using an abrasive cup wheel, always follow the machine builder’s and wheel manufacturer’s safety instructions.

  • Thread the wheel on the machine and hand tighten. Don’t excessively tighten the wheel - removal will be difficult and the wheel could be damaged during removal.

  • Wear all required personal protective equipment such as eye, face, hearing, and respiratory protection as well as gloves, aprons, arm guards and safety shoes.

  • Once a wheel has been mounted, test the machine and wheel by running them under a workbench or in a steel drum for 60 seconds. During the test, keep yourself and your co-workers in a safe area. If there are any unusual vibrations or noises, do not use the wheel to grind.

Using Abrasive Cup Wheels

After you have mounted your cup wheel, follow these best practices to ensure a smooth and safe operating process:

  • Never grind on the outside of a cup wheel.

  • Never abuse the wheel; don’t bump or drop it. If a wheel looks damaged, remove and discard it.

  • Always introduce the wheel to the work gently. Don’t jam the wheel into the workpiece or “force grind” so that the grinder motor slows noticeably.

  • Always store wheels and machines with care between uses. Damage can occur from a drop or other impact just as easily as from improper grinding technique.

  • Always repeat the startup sequence when you get back to work, even if you were just grinding five minutes ago – you never know if something got misaligned while you were away from the workbench.

  • Always pay attention. Never drift away or allow yourself to get distracted while grinding, as the cup wheel can break if not used properly.

For more information on this topic or any other grinding wheel safety information, please review ANSI and OSHA requirements and literature provided by the grinding wheel and machine manufacturer. You may also contact the Saint-Gobain’s Product Safety Department at (508) 795-2317, or you may contact your Saint-Gobain representative with any questions related to safety.