Help needed with disasembly of Mitutoyo Micrometer head
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    Default Help needed with disasembly of Mitutoyo Micrometer head

    Hello all,

    I need to remove the thimble off a high precision Mitutoyo micrometer head. Its part of the stage controls of a Scanning Electron Microscope, and we need to replace vacuum seals for it.

    However, since we managed to lose the manual on how to dissemble the micrometer, i thought id give this forum a try and see if anyone knows how to safely remove the thimble from the head.

    Unlike a normal measurement micrometer there is no ratchet on the end of the thimble, instead its just a thumbscrew.

    The reason im looking into the removal of the thimble is due to the micrometer head blocking access to the fasteners holding the o-ring against the shaft of the micrometer head.

    Here are pictures of the micrometer heads in question:
    20180220_111454.jpg20180220_112434.jpg20180220_112807.jpg

    don't be fooled by the reflection from the door of the microscope.

    edit: i should probably add that i had removed one of the thumbscrews before i took the pictures, i do infarct have it.

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    I had to do this once. I believe the large flat disk that looks like an end cap rotates off? I think I used the little wrench that comes with it to break it loose.

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    Check out the Mitutoyo Small Tools Knowledge Base. Once you register, you can access all kinds of information about their small tools, including owner's manuals and exploded diagrams with parts lists. Mitutoyo America SmallTools Knowledgebase

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    I was pretty sure that the thimble was sitting on a tapered shaft so I guessed at the model number (153-301?).

    PDF Here: https://www.mitutoyo.co.jp/support/s....pdf#toolbar=0

    The usual method to get the thimble loose is to loosen but not remove the thumb screw then hold onto the thimble and smack the thumbscrew rather sharply with a wooden object like a hammer handle. This is done after removing the unit from the machinery of course. The impact will drive the taper out of the thimble. Once the taper is released just remove the thumbscrew and it will come apart.

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    Well, i got the thimbles off, interestingly enough it got them off by turning them abruptly.

    Now a problem has arisen, i was under the impression the shaft was bound by a damaged o-ring seal.

    Now that i have removed the micrometer, i find it seized up.

    I spoke to a friend of mine about this, and he recommended i submerge the front part of the micrometer (containing the anvil) into a ultrasonic cleaner for a few min, shaking lose the thread.

    However, if this works, what sort of lubricant should be used for the micrometer, and or what other method should i use to unbind the screw.

    Funny enough the machine its from has a third micrometer, one that works perfectly. I just found that amusing.

    Here is the partially dissembled micrometer head:
    20180314_154857.jpg

    edit:
    The heads model is "152-348"
    Last edited by omegahyperion; 03-14-2018 at 11:40 AM.

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    Use Starrett Tool Oil to lubricate it.

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    Quote Originally Posted by crazygoat View Post
    Use Starrett Tool Oil to lubricate it.
    I have ordered a bottle. I have talked to a friend who is familiar with equipment like the one im working on, and asked about the possibility of completely unscrewing the micrometer screw. To which he replied "It is nearly impossible to screw the spindle back into the head without fiction. Dont DO IT!" He stated i should partially unscrew the spindle on one side, oil it, screw it back in, and unscrew it partially on the other side, doing the same.

    I would like to know your guys opinion on this, the manual for the machine dose state to fully unscrew the spindle from the head, in order to service the seals. (this was not possible, as the screws had seized up).

    Im honestly a bit unsure as to which approach i should do. I most certainly don't want to destroy the micrometer heads, as a replacement would be a bit expensive.


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