SPHEROMETERS

Page 3.

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There is a difference of .00001" in the sagitta reading. Now I made up a few spherometers. The bars were drilled on the Bridgeport where centres can be set to .0004". However drilled holes can go anywhere and a reamer follows the hole. But as the centres were to be measured after this did not matter. My Bridgeport is a metric machine and (1&2) were drilled at 140mm. (5.5118 ), (3) at 100mm.(3.937"), and (4&5) at 30mm (1.181'). Compare these with the measurements made over the pins and balls. Balls were set in place with Loctite 770 (Superglue). The drawing below shows the design of one of the spherometers. Note how the ball centre is above the surface of the bar so that a measurement can be made over them. Ball diameter was measured as .2497". Measurements were made for:D" on all and recorded. These were made with new Mitutoya verniers. plain and digital.

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