Roger E. Cloutier, Senior Product Safety Engineer
Saint-Gobain Abrasives, Inc.
GOING, GOING, GONE!
We are often asked the questions, "When is a grinding wheel worn out?" The answer depends on the grinding wheel and the application. Listed below are some of the most common types of grinding wheels and the answer to this question.
Type 1 (Straight Wheels)
ANSI B7.1-2000 says, “The usable portion of an abrasive wheel shall be considered to be that portion which extends beyond the mounting flanges. A wheel shall not be worn down to a size which would allow the mounting flange assembly to contact the work piece or work piece holding fixture." This rule assumes the proper flanges are being used and the correct machine guarding is in place. WARNING: You should never grind with the fine center of a wheel and if you are using a super abrasive (diamond) wheel do not grind with the wheel’s core.
Type 2 or Cylinder Wheels and Segments
The machine will determine discard size i.e. the down-feed mechanism will keep the wheel from contacting the work piece. WARNING: Always use proper mounting procedures when using this type of product. Do not loosen mount and lower wheel or segment below the machine’s designed clamping mechanism, i.e. clamping mechanism must have full contact with wheel or segment. This is a major cause of wheel/segment breakage.
Type 5 & 7 (Recessed Wheels)
Wheels that have recesses CANNOT be worn down to their mounting flanges because the edge of the recess will “spall” away. For Types 5 & 7 recessed wheels factors such as wheel grit size, application and experience will provide the user with the best answer. If you do not know, a good “rule of thumb” is to discard the wheel when you are 1” away from the recess.
Type 6 & 11 (Portable Cup Wheels)
Portable cup wheels must be discarded when the machine’s guard prevents proper grinding. In this case a proper guard will determine discard size by preventing additional grinding on the wheel’s rim. WARNING: Never remove a worn cup wheel from its proper grinder and use it on an inline grinder or any other machine. Never grind on the outer periphery of a cup wheel!
Type 6 & 11 (Cup Wheels for Precision Applications i.e. Fixed Based Machines)
On fixed based machines with non-portable cup wheels you should never allow contact with the back of the cup wheel or allow the mounting flange assembly to contact the work piece holding fixture. WARNING: Maintain a safe distance to prevent accidental contact with the back of the cup or the mounting flange during grinding.
Type 27, 29 or Raised Hub Wheels
As with portable cup wheels, the proper guard for Type 27, 28 or raised hub wheels will often determine the wheel discard size. If the application allows the wheel to be worn to stub, you must stop before contacting the mounting flanges and should never use the wheel’s hub to grind.
More about grinding wheels:
For additional information on this topic or if you need any other abrasive safety information, please review ANSI, OSHA and all literature provided by the abrasive wheel and machine manufacturer. You may also contact the Saint-Gobain Product Safety Department at Tel. (508) 795-2317 or Fax. (508) 795-5120, email to firstname.lastname@example.org or contact your Saint-Gobain Abrasives, Inc. representative with any safety related questions.