Hutch,
I don’t know exactly what you mean by 118% of idle speed however what OSHA says is that the wheel can not be run at a velocity (rpm) which exceeds the marked maximum rpm on the wheel, No need to calculate anything just read the maximum wheel speed and be sure the spindle speed does not exceed that (rpm higher than the wheel rpm) don’t spin it faster than that. I have seen too many accidents and fatalities which resulted from wheels exploding due to excessive speeds.
You can see all the entire OSHA regulations also called “Standards” at the OSHA website:
www.osha.gov more specifically the regulation on abrasive wheels is codified 1910.215 and is located at :
http://osha.gov/pls/oshaweb/owadisp...S&p_id=9839&p_text_version=FALSE The specific reference state on this issue states
“1910.215(d)(1)
Inspection. Immediately before mounting, all wheels shall be closely inspected and sounded by the user (ring test) to make sure they have not been damaged in transit, storage, or otherwise. The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel. Wheels should be tapped gently with a light nonmetallic implement, such as the handle of a screwdriver for light wheels, or a wooden mallet for heavier wheels. If they sound cracked (dead), they shall not be used. This is known as the "Ring Test".”
Additionally many accidents result from missing guards particularly the tongue guard which must be adjusted to within 1//4 inch of the periphery of the wheel (obviously needs to be readjusted as the wheel wears).
The other most frequently found problem is the work rest which must be adjusted to within 1/8 inch of the periphery of the wheel.
BTW the “ring test” is used to detect unseen cracks in the wheel which would also cause the wheel to explode upon starting. When tapped with a wooden dowel the wheel should have a distinctive ring or resonance not a dull thud . A dull thud would indicate a crack or cracks in the wheel and the wheel should not be used. Also never stand directly in front of the wheel / grinder when turning it on the first time after mounting. This is the most likely time that the wheel will explode if anything is wrong (cracks in wheel, incorrect mounting etc) .
And that’s the gospel according to OSHA, hope this helps. OSHA Professor – Grizzy
