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  • Digital Calipers

    As a low-budget home machinist, I am wondering about two things:

    1: Just how useful are digital calipers? I have a 0-1 mike and a depth gage mike, but no non-junky slide calipers of any kind.

    2:How useful is a test indicator if you have a dial indicator (a Starrett, no less! it was a hand-me-down) and a homade gizmo that gives you a side lever?

  • #2
    Calipers are pretty nice for general measurements like verifying the size of the stock you're grabbing. They're just way quicker than a micrometer and if I don't need to measure to the tenth then I grab the calipers. I've got a couple of Harbor Freight digitals, a Mitutoyo dial caliper, and a 12" vernier caliper in my arsenal. The HF digitals are OK, although one of them really doesn't repeat well at all. I'm constantly zeroing it and after a few measurements it's off by .0005 one way or the other and gets worse from then on. The other one is fine though.

    Edit: I can't live without my test indicators because I do almost all of my work with a four jaw chuck. Also indispensable for tramming you mill head. I have a .0005 and a .0001, which I use far less frequently.
    Last edited by hornluv; 08-19-2008, 09:02 PM.
    Stuart de Haro

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    • #3
      Yes! Calipers are very very handy. However, don't buy cheap ones! I personally favor dial calipers for reasons I've mentioned in numerous other posts about digital vs analog. Digital are nice too, but I'm just "old school". Anyway, mine are a fully jeweled mitutoyo 6" calipers and they get used all the time. They are hard to find these days, most of them are not fully jeweled and they feel different. I've gotten spoiled with my pair and using non-jeweled feel rough and inaccurate. Its just a feeling - there is nothing really wrong with them.

      As far as a DTI goes, what is the resolution on the DI? I currently have a DI with a .5" range and a .0005" resolution. That works ok with a homemade "side lever thingy" as you call it but a DTI is much nicer. Its not a neccessity as long as you have a DI that reads to .0005, but its definitely a perk. I'm looking at buying a mitutoyo DTI with .0001" res. Its a pretty decent price at Enco, actually.

      Edit: Just read Hornluv's edit! With a mag base, the DI works great for centering work in a four-jaw but for tramming a mill head or indicating a vice in, a DTI is a must. (Or at least a goofy adapter so you can hold the DI in the spindle and read the dial still. I've made an adapter, but a DTI is much much nicer)

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      • #4
        Like any measuring tool, calipers have their place.
        Also, any precision tool must be calibrated, and checked against standards.

        NEVER trust a caliper to read inside a hole, (to any precision). They are off by varying amounts depending on the diameter of the hole.

        I have several calipers, vernier-dial-digital spanning the last 40 years. If I need better than .004", I use a calibrated micrometer, or check the caliper calibration AT THAT DIMENSION, keeping in mind that +-1 digit is typical repeatability.

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        • #5
          I leave a couple of cheap harbor freight 6" dial calipers laying out all of the time. I don't use them for inspection, but they are great for general measuring and converting inch to metric measurements. You can catch them on sale for about $10 so if they get dropped it is not the end of the world, and accuracy wise, I have yet to see a problem, but I do regularly calibrate them against my Cadillac gauge just to keep them honest.

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          • #6
            Remember that the digital calipers have a resolution of 5 tenths, but an accuracy of 2 thou.
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • #7
              Originally posted by ikrase
              1: Just how useful are digital calipers? I have a 0-1 mike and a depth gage mike, but no non-junky slide calipers of any kind.
              I have two Mitutoyo digis at work, and they're worth it. 6" and 8", both accurate to a thou. In my opinion, you can easily feel when a caliper isn't going to give you the accuracy you need. No Mitutoyo calipers I've seen have ever failed to be accurate to at least a thousandth. Can't speak for other brands.

              The knife edges on my 8" are sharp enough to measure down to about .090" holes accurately, backed up by pins and a CMM.

              Originally posted by ikrase
              2:How useful is a test indicator if you have a dial indicator (a Starrett, no less! it was a hand-me-down) and a homade gizmo that gives you a side lever?
              Test indicators are amazing. I reach for them way, way more often than a dial indicator. I don't see how any gizmo on a dial can compete - you can move the stylus on a DTI to give you any convenient angle, which I find helps enormously.

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              • #8
                Originally posted by toastydeath
                I have two Mitutoyo digis at work, and they're worth it. 6" and 8", both accurate to a thou. In my opinion, you can easily feel when a caliper isn't going to give you the accuracy you need. No Mitutoyo calipers I've seen have ever failed to be accurate to at least a thousandth. Can't speak for other brands.
                Ditto. I have the Mits IP65 calipers, and they're sweet. I don't know how much more accurate they are than the Chicom calipers, but they weigh nearly twice as much as my Horror Freight specials

                Penn Tool often has the Mits calipers on sale...
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  Originally posted by toastydeath
                  No Mitutoyo calipers I've seen have ever failed to be accurate to at least a thousandth. Can't speak for other brands. .
                  Yep! I posted a thread a little while ago about repairing my Mitutoyo and once I got it back home again, I checked it at 1", 2", 3" and 4" using the gauges that came in my micrometer set. They were accurate at all of those lengths to within a thou. The needle was visible off of the 0 mark at 4". The other dimensions and it was nearly dead on. But yes, they do have their place.

                  Originally posted by toastydeath
                  I don't see how any gizmo on a dial can compete - you can move the stylus on a DTI to give you any convenient angle, which I find helps enormously.
                  Those gizmos can't compete, but they are much cheaper I think Ikrase is in High School or maybe a freshie in college this year. Either way, even 20 bucks seems like alot when you don't have a regular income!

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                  • #10
                    i have 2 O-1 jobbies and 3 sets of digitial calipers and i do prefer the digitial calipers but iam also not working in that close of tolerences either

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                    • #11
                      Originally posted by lazlo
                      Remember that the digital calipers have a resolution of 5 tenths, but an accuracy of 2 thou.
                      The Harbor Freight 6" calipers I own all say they are"Accurate to .001" and have a resolution of .0005". In my occasional checking with gage blocks I find they are accurate to that degree, however, if I am getting that close I will usually check with a mic. I really like digital calipers. They are certainly convenient to use.

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                      • #12
                        Originally posted by Philt
                        The Harbor Freight 6" calipers I own all say they are"Accurate to .001" and have a resolution of .0005".
                        Take another look -- they say "accurate to +/- .001"

                        This is the manual sheet that comes with the Harbor Freight calipers:

                        Last edited by lazlo; 08-19-2008, 11:56 PM.
                        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                        • #13
                          I have three pair 8" Mitutoyo digitals,two of the digimatic and one of the IP67.
                          .

                          The digimatic calipers are better IMHO.The IP67's they dropped the floating zero function and the on/off button.The floating zero was like a mini DRO,set the dimension you want and zero the scale,each measurement you take then on is the remaining material to be removed.Handy feature if you get interrupted a lot.

                          Accuracy,well no caliper is as accurate as a mic,but both are comparison measuring tools,not standards.

                          Calipers can be quite accurate once a feel has been developed and the use of ring gauges and space blocks augments that.

                          These don't have to be anything expensive either.Some bearing inner races of various size come in as handy ring gauges.Outside mics set to the finished dimension work well too.
                          I just need one more tool,just one!

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                          • #14
                            Originally posted by wierdscience
                            The IP67's they dropped the floating zero function and the on/off button.The floating zero was like a mini DRO,set the dimension you want and zero the scale,each measurement you take then on is the remaining material to be removed.
                            Wierd, there are several Mits IP67 calipers. My silver ones have the floating zero -- they call it "Origin." They don't have an on-off, but that because they have auto-off after 5 minutes or so.
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                            • #15
                              Well, after all of this talk about calipers, I started wondering when I checked the "lay around" ones was, and I could not really remember. I found 3 laying around and checked with my Japanese Fowler 1" and 2" calibration blocks and my good 123 blocks. 2 of them were spot on and the 3rd was consistantly off by .0005" over on 1", 2", and 3". I feel better now about not wanting to pull out my good ones except for real jobs. Somewhere around here I have a 12" Mitutoyo that I saved a lot of lunch money for that has a nice bend in it from being under some shop towels that I set a 6" vise down on. The replacement set stay in their wooden box except for special times.

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