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Sunday, 24 November 2013

Inspection Methods of Grinding Wheel

Inspection Methods of Grinding Wheel Points : Inspection Methods of Grinding Wheel, Speed Testing, Checking the Grade, Wheel Balancing As soon as grinding wheels are received, they should be closely inspected td make sure they have not been injured in handling or shipping. Cracks can be detected by tapping the wheel gently with the handle of a screwdriver while the wheel is suspended. If the wheel sounds cracked, it should not be used. All wheels do not produce the same tone when rung; nor does a low tone signify a cracked wheel. Vitrified and silicate wheels emit a clear metallic ring; organic bonded wheels give a less clear sound, but the sound of a cracked wheel will le perfectly apparent. Oil or water-soaked wheels do not ring clearly. The wheels must be dry and free from sawdust when the test is applied. Otherwise the sound will be deadened. Speed Testing Wheels 152.4 mm (6 in.) in diameter and larger are given a speed test. Then are run, under a hood, at a rate of at least one and a half times the recommended speed. This gives a stress of more than double that which is given in actual practice. Checking the Grade This is commonly done by hand, by slightly twisted a short screw-drive-like tool into the side of the wheel. The resistance offered, compared with the resistance of the bond in a wheel of known grade, indicate the grade. Wheel Balancing The point which deserves attention on all grinding Operations except the very roughest is the balance of the wheel, and before mounting, the wheel should, if possible, be tested for balance. This can be carried out with the wheel mounted at the center of a perfectly straight and round spindle, assembly then being, rested on level knife-edge ways or on a lathe bed. For the test to be really satisfactory the wheel should be mounted on its own spindle and the test made after truing up the wheel face. Balance maybe achieved by:
1. Adding weight in t form of lead to the light side. This may be accomplished by removing small amounts of the wheel beneath the flanges and, then filling the holes thus made with lead.
2. On some wheel units, balanced is achieved by adjustment of segments attached to the inner sleeve flange.

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