Question

how is the pitch found​

Answer 1

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• In use, the pitch is formed into a lap or polishing surface, which is charged with iron oxide (Jewelers' rouge) or cerium oxide. The surface to be polished is pressed into the pitch, then rubbed against the surface so formed.
• Pitch of the screw gauge is defined as the distance moved by the spindle per revolution which is measured by moving the head scale over the pitch scale in order to complete one full rotation.