# Advice On Repairing A Mitutoyo Micrometer



## clevinski (Feb 27, 2015)

Hello, All,

I just purchased a used Mitutoyo 1-2" micrometer at an estate sale for $20.  The model number is 102-226.  The issue is that the portion of the micrometer sleeve that you normally grasp to turn is loose.  If I grip the portion of the micrometer which has the calibrated markings on it, this seems to turn correctly.  But the rear portion that normally contains the clutch has about .015 inches of axial play.  In addition, when turning this clockwise (i.e., closing the faces), it stops with almost no force.  Turning counterclockwise, there seems to be no clutch action at all.

I disassembled the clutch, and find inside a spring anchored to the body on one end, with no connection on the other end.  This is what seems to be causing the one-way rotation action.  My sense is that something is missing.

I've attached two files showing the disassembled micrometer and a close-up of the spring.

Any advice on how to repair the clutch mechanism would be appreciated!

Thanks,
Charlie


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## JimDawson (Feb 27, 2015)

It sounds like it is working normally.  The spring is a one-way clutch.  It should lock when opening, and almost freewheel when tightening.  That provides the correct force to get consistent readings.

The axial play in the thimble sleeve is normal.


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## darkzero (Feb 27, 2015)

Agreed, sounds like it's working as normal. What you have is known as a friction thimble, not to be confused with the ratchet thimbles (the type that clicks). I actually prefer the friction thimbles as some ratchet mechanisms are too harsh depending on the make/model.


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## clevinski (Feb 27, 2015)

Thanks for the replies... I think what surprised me was the very small amount of force needed for the clutch to slip while closing.  It is less than any other mic that I own, but that may be a good thing.

Thanks again for the prompt answers!

Charlie


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