CMM1
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Optical Polygon, manufactured by Hilger & Watts. Has twelve faces, 30 degrees apart in a horizontal plane. Used with an autocollimator for calibrating dividing heads and coordinate measuring machines. A used example is on sale at another web site at $4200. Mint condition; no marks or fingerprints on the reflecting surfaces. Serial No. 200405; comes with calibration sheet signed in ink by QA manager of Webber Gage Division of Starrett dated 2/8/96. Greatest deviation is 1.6 seconds of arc. Stout custom-made polymer box. E-mail me at
image of email address
to obtain an image of the calibration sheet, which was printed by a dot matrix machine and whose scan is only readable in high-resolution format.  Price: SOLD
The optical polygon is used by placing it on a shaft that is concentric with the rotation axis being checked. The diameter of the through hole in the device is approximately 5/8 inch; I can check the exact inside diameter with plug gages on request.