Poor mans lathe DRO's

[Saltfever]

. . . If you're going to check a micrometer for accuracy, it's important to use a set of gage blocks that cause the spindle to seat at different orientations so drunken thread errors will be noticed. The preferred set for inch micrometers is: 0.105, 0.210, 0.315, 0.420, 0.500, 0.605, 0.710, 0.815, 0.920, 1.000 . . . .

Marv, I notice your preferred increment is 0.105" each time. On a typical 40 thread mic that would be 4.2 threads. Anything special about 4.2 threads every time?

[mklotz]

Marv, I notice your preferred increment is 0.105" each time. On a typical 40 thread mic that would be 4.2 threads. Anything special about 4.2 threads every time?

As the quote says, it's done so the spindle seats at different rotary orientations each time. The last thing one would want is an increment (such as an integer multiple of 1/40 = 0.025) so the spindle always seats at the same orientation.