Hazards – Blog I am often asked about some of the hazards I generally found during inspections. These are by far the most frequent hazard I found while conducting inspections. Most of them are actually very simple to fix. It really boils down to training your employees in some of the OSHA rules
Description: A bench grinder in the maintenance shop was not safeguarding to OSHA’s minimum requirements. OSHA requires the following items with respect to bench grinders:
Tool rests (work rests) shall be kept adjusted closely to the wheel with a maximum opening of 1/8” to prevent the work from being jammed between the wheel and the rest.
Tongue guards shall be kept adjusted to within 1/4” of the outside of the grinding wheel to deflect fragments away from the operator should the wheel shatter.
As the bench grinder is designed for a fixed location, it must be securely anchored to prevent walking or moving during operation. (1910.212b)
Immediately before mounting, all abrasive wheels are to be closely inspected and sounded (ring tested) by the user to make sure they have not been damaged in transit, storage, or otherwise.
Condition: Work rests. On offhand grinding machines, work rests shall be used to support the work. They shall be of rigid construction and designed to be adjustable to compensate for wheel wear. Work rests shall be kept adjusted closely to the wheel with a maximum opening of one-eighth inch to prevent the work from being jammed between the wheel and the rest, which may cause wheel breakage. The work rest shall be securely clamped after each adjustment. The adjustment shall not be made with the wheel in motion. Exposure adjustment. Safety guards of the types described in Subparagraphs (3) and (4) of this paragraph, where the operator stands in front of the opening, shall be constructed so that the peripheral protecting member can be adjusted to the constantly decreasing diameter of the wheel. The maximum angular exposure above the horizontal plane of the wheel spindle as specified in paragraphs (b)(3) and (4) of this section shall never be exceeded, and the distance between the wheel periphery and the adjustable tongue or the end of the peripheral member at the top shall never exceed one-fourth inch. (See Figures O-18, O-19, O-20, O-21, O-22, and O-23.) 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".
Standard: 1910.215(a)(4), 1910.215(b)(9), 1910.215(d)(1)
Potential Effects: Cuts to fingers and penetration injuries from contact with or disintegration of the grinding wheel.
Recommended Action: Ensure the grinder is bolted to the bench and adjust the tongue guard and tool rest to the specifications listed above. As the wheel is ground down, readjust the guards. This adjustment should be checked routinely before energizing the wheel, as a standard safe operating procedure. Ring test stones.
Procedures for ring test stone: To conduct the ring test on smaller wheels, they should be tapped lightly with a light nonmetallic implement, such as the handle of a screwdriver for light wheels, or a wooden mallet for heavier wheels. Tap wheels about 45 degrees each side of the vertical center line and about one or two inches from the periphery. Then rotate the wheel 45 degrees and repeat the test. A sound and undamaged wheel will give a clear metallic tone. If cracked, there will be a dead sound and not a clear "ring." If they sound cracked (dead) they must not be used. Wheels must be dry and free from sawdust when applying the ring test, otherwise the sound will be deadened. It should also be noted that organic bond wheels do not emit the same clear metallic ring as do vitrified and silicate wheels.
Larger wheels may be tested by vibration to detect damage. To perform the vibration test, an abrasive wheel is set on a test fixture in a horizontal position and coated with a thin layer of fine dry sand. The wheel is vibrated gently. As the wheel vibrates, the sand granules respond to the vibration. The granules will move away from any cracks that may be in the wheel. Conversely, the granules will be uniformly distributed over the surface of a sound and undamaged wheel.
Note that the spindle speed of the machine must be checked before mounting the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel.
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Author: Deborah Grow, Safety Specialist
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