How Often Must I Check the Speed of a Grinding Machine?
Before we start, let us make it clear, EVERY time a wheel is mounted or remounted onto a machine the operator must check the wheel and machine's speed to make sure the wheel is not operated in an over-speed condition. The abrasive wheel's safe operating speed in marked on the wheel and the machine's normal operating speed is marked on the machine. NEVER exceed the wheel's safe operating speed as stated in Revolutions Per Minute (RPM) or in Surface Feet Per Minute (SFPM). Failure to comply with this requirement is not only very dangerous, but is also a violation of ANSI safety requirements and OSHA law.
ANSI B7.1 -2000 has the following requirements for when machine speed must be checked:
7.2 Speed Check of Machines - User's Responsibility (The Requirement)
The user shall establish a program to ensure that grinding machines do not subject abrasive wheels to speeds greater than the maximum operating speeds marked on the wheel or package. In the case of variable speed machines the number of revolutions per minute (RPM) may be increased as the diameter of a wheel is reduced through wear, provided the original surface feet per minute (SFPM) is never exceeded (the speed table in section 10, table 35, will be helpful in converting RPM to SFPM, also see section 1.2.88, page10). It shall be the user's responsibility not to exceed these maximum operating speeds. Spindle speed shall be measured at free running speed of the machine.
E 7.2 Speed Check of Machines - User's Responsibility (Explanation of the Requirement)
It is of special importance that portable air grinders should be checked to be sure that proper air pressure is maintained and that the machine governor mechanism is clean, in good operating condition, and functioning properly. This reference to air grinders is not intended to overlook the necessity for a regular check of the speed of the wheel spindles on all typed of grinding machines. The user should assign this responsibility to competent personnel using equipment properly designed for speed check purposes such as a tachometer or stroboscope. the user should also keep a permanent record of such speed checks. A tachometer is suitable for use on the majority of machines to check the spindle speed (RPM). From a safety standpoint this tachometer check should be made without the grinding wheel, loose flange, or nut mounted on the spindle.
Air Driven - Measure the speed of governor controlled grinders every 20 hours of actual use or once per week, whichever comes first. Measure speed of all types of grinders after maintenance or repair, whenever a grinder is issued from the tool crib and at each wheel change. Several readings should be taken.
Electric Driven (Hi-Cycle) - Measure monthly and after any maintenance or repair that could affect the speed of the machine.
All Other Grinders
Direct Drive (Single Speed) - Measure after any maintenance or repair that could affect the speed of the machine.
Belt Driven (Single Speed) - Measure monthly and after any maintenance or repair that could affect the speed of the machine.
Variable Speed Machines - Measure once per week and after any maintenance or repair that could affect the speed of the machine. On variable speed machines, other than semi-automatic snagging grinders, measure speed whenever a wheel change is made.
Knowing and following the ANSI/OSHA rules will keep you safe at the wheel! We are hoping all your grinding wheel usage is safe and productive.
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 or contact your Saint-Gobain Abrasives, Inc. representative with any safety related questions.