Index plate

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a graduated circular plate, or one with circular rows of holes differently spaced; used in machines for graduating circles, cutting gear teeth, etc.

See also: Index

References in periodicals archive ?
Other safety features include an integrated electric position indicator in the mounting flange that visually shows whether the valve is open or closed and an index plate that clearly indicates the angle opening in degrees.
The parts molded in the upper index plate rotate down to the center area, while the parts molded in the lower index plate rotate up to the same center area, so the mating parts end up face to face.