OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

June 20, 1984

Mr. J. J. Wherry
Grinding Wheel Institute
712 Lakewood Center North
14600 Detroit Avenue
Cleveland, Ohio 44107

Dear Mr. Wherry:

This is in response to your letter of May 10, 1984, to Mr. Ken Yotz of our Chicago Regional Office. Your letter pertains to the acceptance by Occupational Safety Health Administration (OSHA) of certain threaded bushings on type 11 grinding wheels as being safety guards.

As you are aware, OSHA adopted the ANSI B7.1-1970 consensus standard and incorporated that standard into 29 CFR 1910 as 1910.243(c). 29 CFR 1910.243(c)(2)(ii) permits the use of "revolving cup guards," as did the ANSI B7.1-1970 standard. Since that time, the ANSI B7.1 committee has eliminated mention of revolving cup guards but has not prohibited their use. OSHA has not updated this standard and therefore continues to permit "revolving cup guards" as acceptable safeguards.

The standard for revolving cup guards specifies certain minimum physical requirements for their application. It has been determined that some configurations of "threshold bushings" accommodate the requirement for revolving cup guards in that they are "made of steel or other material with adequate strength and enclose the wheel sides upward from the back for one-third of the wheel thickness." In these instances threaded bushings become, in fact, revolving cup guards and an integral part of the device. The need to maintain a clearance of up to 1/16 inch between the wheel and guard becomes a superfluous requirement and not a consideration for such integral devices.

Under our standard, therefore, OSHA must accept the use of integral revolving cup guards including appropriately configured safety bushings. However, if manufacturers declare and label the units equipped with "safety back bushings" as not constituting an equivalency to "revolving cup guards" in that their dimensions and/or strength do not conform to the requirements of 1910.243(c)(2)(i)) insist upon safety guards such as those recommended by the ANSI B7.1-1978 standard.

Should statistical data become available verifying your concern for the continued use of revolving cup guards, OSHA would further explore the need for a modification of the standard.

If we may be of further assistance, please contact us.


John B. Miles, Jr., Director
Directorate of Field Operations