Grinding Wheels - 8: Identification
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.
Each grinding wheel comes with a paper label glued to its face. The label provides much information concerning the composition of the wheel.
The system is a series of numbers and letters which codify the composition of the wheel. The first letter indicates the type of abrasive used, using the letter A for Aluminum Oxide or C for Silicon Carbide. Next the manufacturer of the wheel will indicate the grain size, with appropriate numbers indicating a coarse, medium, or fine range. The grade is indicated in alphabetical form, with the softest grade being the A end of the alphabet, and the Z being the hardest.
Structure is indicated by a numerical rating, but its use is optional. Finally the bond type is indicated by an abbreviation of the type of bond used, V for vitrified, S for silicate, etc.

Wheels sometimes have different colors and can be representative of the type of wheel. If the Norton Company is used as a reference, the following color codes would apply for the best materials and processes for each wheel:

  • White Aluminum Oxide - Used on tool steels and mold steels
  • Pink or Blue Aluminum Oxide - Used on alloyed tool steels
  • Off-White/Light Grey Monocrystalline Aluminum Oxide - Better for holding than the above, used on high speed steels as well
  • Light Blue Synthetic Aluminum Oxide - Works on all ferrous materials, used in high production applications
  • Gray Mixed Aluminum Oxide - Used on centerless or cylindrical applications
  • Green Silicon Carbide - Used on non-ferrous materials such as aluminum and carbide tooling.

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