Starrett Depth Micrometer

I have a set of Starrett depth mic's. These are the rod type and I need to know how to zero the thimble. I am using a gage block and a surface plate. There doesn't seem to be anywhere where the graduated spindle turns like it does on an outside mic. Also, the wrench that fits the nut inside of the thimble seems to adjust the pressure required to turn the thimble. The only other thing I can think of adjusting is the stop nut on the rod. These seem to be loctited on and are not movable. Any advice on getting these zeroed would be greatly appreciated. Thanks, Steve

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I can't say for certain on the Starrett mic's but every other depth mic I have come across, you have to adjust the nut on the rods. Otherwise if you adjusted the mic for one rod, it would be out on the rest. Try some gentle heat from a hot air gun to loosen the loctite, or if you can get it, some solvent for a day or two. If you do get it loose, try and use 2 sets of gage blocks to support the mic when adjusting it. This will reduce the possibility of error from tilt, and you wouldn't have to hold on to it at all times.

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You adjust it by moving the nut. I don't think they are Loctited, but the thread fit is very tight. You can move the nuts with a close fitting wrench.


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R. O'Brian

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