Measuring small parts

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  • Measuring small parts

    Sorry, I cannot post a print for this question.

    I am constantly being asked to measure parts that have features that are less than 0.100". While I have been able to figure out how to do this reliably enough for a few parts (stick them on 2-sided tape and such), I've had to turn away several requests. Those that I've declined are on the order of 0.070" all the way down to a 0.023" slot and radii of 0.008" (that part is 6mm x 4.5mm x 1.5mm.(!)) I commonly use a 27 x 1mm probe.

    The smallest probe I can even order is 0.3mm dia., but it is so short I don't even know how I'd use it. 7mm x 0.5mm dia. seems more practical, but is it worth it? And even at that, I think I would also need a low force probe body. This is on a D-12 with a PH10T head and a TP20.

    I think in the end these people need to find a different (optical?) method of measurement (which we have on hand).

    Am I right, or do I just not know the capability of my machine?
    (please help me stick to my guns )

    Are there other complications with measuring features that small? I have trouble trusting a measurement on a part I can barely hold.

    Thanks,
    J

  • #2
    I was taught to measure holes that are at least 2x the size of your ruby tip. That would make the smallest hole 2 mm or .0787 inches. Even then I have found that the accuracy is questionable. Open setup is what I use for small parts and I get great results.

    Hope this helps... Just my humble opinion.
    Actively looking to be a CMM guy again
    Previously 4.3 MR2
    XP OS

    Is your problem a case of operator headspace?

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    • #3
      I use a 4mm(.157480315") size ruby to check .205" holes everyday and get great results......
      sigpic

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      • #4
        I use a 0.3mm for 95% of the parts we measure. (Internal configurations of dental implants).
        If you are going to be doing multiple parts than custom fixtures are going to be something that you need to invest in. If this is for 1 part or short run parts than the investment may outweigh the cost.
        I am fortunate that I have a machine shop were we build our own fixtures.
        Touch speeds, move speeds all need to be slowed down.
        R&R tests will be the only way you can be assured of your measurement process.
        Good luck.

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        • #5
          Originally posted by jstrau View Post
          I use a 0.3mm for 95% of the parts we measure. (Internal configurations of dental implants).
          If you are going to be doing multiple parts than custom fixtures are going to be something that you need to invest in. If this is for 1 part or short run parts than the investment may outweigh the cost.
          I am fortunate that I have a machine shop were we build our own fixtures.
          Touch speeds, move speeds all need to be slowed down.
          R&R tests will be the only way you can be assured of your measurement process.
          Good luck.
          That's where I felt I was heading. But like you said, the investment may not be worth it, esp. since we do already have optical means on hand (although sometimes optical requires cutting the part - but they are cheap parts).
          Very helpful!
          Thanks,
          J

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          • #6
            If your doing a lot of slots, grooves, internal radi, get a Dupli-cast putty kit.

            I know there a joke here somewhere.
            Cookie

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            • #7
              Originally posted by Cookie View Post
              If your doing a lot of slots, grooves, internal radi, get a Dupli-cast putty kit.

              I know there a joke here somewhere.
              Thanks.
              That is on my radar, too. Not excited about going that way.

              I'll have to find the joke - I'm sure it's educational.

              J

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              • #8
                the only limitation is your imagination and skill. Measure away. you can get custom probes if need be and touch probe anything you have the eyesight, cad model and nerves to measure. Measuring .011" dia holes with .007" (.2) probes is a trick but not a fancy one.

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