Calibrate / Adjust Starrett Digi-Chek 258 Height Gage - Page 2
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  1. #21
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    The story continued. As noted in the previous post, the micrometer's witness mark wasn't centered, which bugged me. In addition, I discovered that I couldn’t get micrometer to go to the 1.1000 position because the top of the stack connector was striking the bottom of the head.
    53c-stack-connector-jammed-against-bottom-head-large-.jpg

    The top of the micrometer's limit was a little beyond 1.050. I screwed in the micrometer .050 which gave clearance between the top of the stack's connector and the bottom of the head. At this point the micrometer was reading 1.000. I wanted to make this setting to be 1.1000, so I needed to remove the micrometer's thimble to reset its height. The thimble is held on with a screw having a flat top with four peripheral notches. I made a 'wrench' to fit this. As it turned out one of the notches was peened narrower than the rest. The previous owner appears to have used both pliers AND a punch on this screw. I tried tapping the offending proud area of metal in the notch with a small punch hoping to displace enough of it that the tool would fit, but better than that, it loosened the screw, which I removed by hand. After this was off, I filed the narrow notch until the tool fit.
    44-tool-w-prongs-next-nut-slots-large-.jpg 45-tool-slotted-screw-loose-i-lifted-mic-off-large-.jpg

    The micrometer's thimble came off with just a little shake exposing the tapered nut on which it sits inside the micrometer body.
    47-screw-removed-insides-micrometer-large-.jpg 48-closeup-insides-mic-blurry-large-.jpg

    I unscrewed the tapered nut until the micrometer was at a height of 1.1000, then I rezeroed the stack. I'd like to say that that was the end of it, but it turned out that when I checked measurements against gage block, they started to vary above 1.0500. This part of the micrometer threads must have been worn. I wound up lowering the micrometer stem a little more and raising the tapered nut a little more until I had measurements that checked from .1000 to 1.1000 I then reset the counter as previously described above and checked the readings with gage blocks at different heights before accepting it as done.

    A couple of extra things I noted along the way (ahem wasted time by making mistakes) Put the two front socket screws in the head before inserting the micrometer because the micrometer blocks these screws. Make sure the micrometer is fully seated in the head before tightening its holding screw. It may be easier to rezero at .1000 than at 1.0000 because the studs for the stack's return springs may interfere with the adjusting nut, depending on the position of the stack on the nut. When I lowered the mic to reset its height it bottomed on the surface plate before I got down to .1000 and of course had to adjust the stack height upward.

  2. #22
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    Glad you fixed yours. But could you show how to use it? Like how to set it up to calibrate a dial bore gage? And other practical uses? Thanks!

  3. #23
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    I fixed mine, but I only have it because I got it inexpensively so I'm not the best person to make a tutorial on all the different ways it's used. With regard to the bore gage however, the typical way you use them is to set your micrometer at the desired measurement, put the bore gage in the micrometer and set zero on the bore gage. If you need to confirm the micrometer is reading correctly, you make a stack of gage blocks of the measurement you want and check that with the micrometer to be sure it's reading correctly. Lacking gage blocks, machine something to the desired measurement, check that on the surface plate with the height gage to confirm it and then check it with the micrometer. Or maybe you already knew all of this, but if not, that's the way I'd approach it. There are often several ways to accomplish the same result.

  4. #24
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    My one is metric and in superb condition. I even have both the Brown & Sharpe and Cadillac gage competitors - also good - to check it against.

    Even so, I thank you - and all-hands who pitched in - for taking the time to sort this one out AND making the extra effort to help save the rest of us having to search for documents to do it all over "alone and in the dark", as the expression goes.

    "PM ...doing what PM does best!"

    Well done, the lot of yah!



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