This Spherometer can be used in metric or inch mode.
Spherometers are used to measure the radius of curvature of the surface of a lens or mirror. The Spherometer has three legs with ball cap nuts on the ends. The Spherometer is 4.25 inches in diameter. The Digital Indicator has 1 inch of total range of travel, with 0.0005 graduations. This Spherometer is extremely easy to calibrate, just set it on a flat and press ZERO. The three legged base should be less than half the diameter of the mirror. This allows the testing of zones across the mirror in addition to measuring the radius of curvature. Includes chart for focal length.
Special thanks to Ken Hunter who wrote the spreadsheet and made it available to the ATM community.