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Thread: Adjusting depth micrometers?

  1. #1
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    Question Adjusting depth micrometers?

    Do they make standards for calibrating depth micrometers? It's easy enough to adjust the 0-1" rod, but I don't have a reference for the others. I suppose 1-2-3 blocks and a surface plate would work, but what is the proper way to do it?

    Thanks,
    Stuart
    Stuart de Haro

  2. #2
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    Default

    I would not count on 1-2-3 blocks to be accurate enough to use as a standard. If you could mic them or otherwise determine their actual dimension, thay could be used.

    Jo blocks could be used as a fixed standard, or a planer gage set to a known, accurate dimension with mics as a substitute.
    Jim H.

  3. #3
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    Quote Originally Posted by hornluv
    I suppose 1-2-3 blocks and a surface plate would work...
    That is exactly what I would use.

  4. #4
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    How about taking the standars used in setting 2", 3", 4" or what ever mike, check them with a mike and then check the depth guage. riceone

  5. #5
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    you'd need two, and some care, but why not?

    The 123 if mic'd would be OK.

    How about the 12" rod (or larger) for an ID mic? THERE is an awkward thing to cal, I'd guess, at least in the home shop.

  6. #6

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    Quote Originally Posted by riceone
    How about taking the standars used in setting 2", 3", 4" or what ever mike, check them with a mike and then check the depth guage. riceone
    The length standards would be accurate, but how would you hold the depth mike and the standard to be square with something like a surface plate? A slight out-of-perpendicularity would introduce a large error for calibration purposes. I believe that I've seen step blocks for setting, but I don't think I'd pay real money for one for just occasional use. Gage blocks would be my choice.
    .
    "Opportunity is missed by most people because it is dressed in overalls and looks like work." Thomas Edison

  7. #7
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    Twin stacks of gage blocks well wrung would be my choice, though a single would do if careful. Or take a calibrated mic and check the required dimension of a 123 (or other) precision setup parallel, particularly one with a hole, and then use to calibrate the depth mic. For a quick sanity check when I swapped the 2" rod into my Starrett DM, I took just took out a "known good" B&S 123 block with holes, wiped it down, wiped down the granite surface plate, lay the block on the surface plate, and checked that I got 2.0000. Seems like it was maybe about a "fuzz" off (tenth or two?), but what did I care? All I wanted to do was make sure there were no gross errors before checking the bottom of a bore shoulder.

  8. #8
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    Quote Originally Posted by riceone
    How about taking the standars used in setting 2", 3", 4" or what ever mike, check them with a mike and then check the depth guage. riceone
    I can't imagine holding the micrometer steady on top of one of those standards. I think the 1-2-3 block idea would work for my purposes. I can just mic the dimension of the block and make sure I get the same reading on the depth micrometer. Thanks for letting me pick your brains!
    Stuart de Haro

  9. #9
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    I don't use a depth mic, but I'm a tech.
    So.... I'd use some sort of continuity test.
    Meter, buzzer, LED.

    Of course, you'd need a standard.
    Or was that what you were asking for?

    edit, sorry, you were asking for a standard.
    hmmmm, gotta be a way
    Just got my head together
    now my body's falling apart

  10. #10
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    Default Keep it simple.

    I presume the OP's depth micrometer is 0 > 4".

    Let's not make it too difficult or expensive.

    If you have a reasonable 0 >4" outside micrometer and a set of "checking sticks" that came with it, you are half-way there.

    Get some precision hot-rolled/extruded tubing - any size or OD between say 1" and 3".

    Cut it off and face it both ends to lengths of anywhere between 1" and 2", between 2" and 3" and between 3" and 4".

    Length doesn't matter but having the ends faced-off and parallel to within 1 or 2 tenths (or better if you can) certainly is. If you only have a solid shaft/rod, drill a hole - any size bigger than the depth mic. rods.

    Material doesn't matter - as long as its metal - steel, brass, stainless etc.

    Use your pre-set/pre-checked 1">2", 2">3", and 3"<4" micrometers to accurately measure the lengths of those pre-prepared tubes and note their lengths - perhaps engrave (by hand) the sizes on them. If they are damaged they are easily restored or replaced.

    Use them to check, and if necessary (re-)set your depth micrometer.

    Put the tubes away for future use or reference.

    It is NOT important the the tubes be any particular length.

    Sometimes too much is made of what is basically a simple requirement and a simple job.

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