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Dial test indicator range question

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  • Dial test indicator range question

    Hello
    I see dial test indicators the read to tenths but only have .008" range. Is that the true range on the indicator? Or is it just the range of the dial ie. needle can make multiple turns but there is no rev. counter?
    Thanks

  • #2
    I have an old Baty which reads in 0.0001" at 0.1" per turn which has a second small dial for up to 0.5" total travel.

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    • #3
      Originally posted by old mart View Post
      I have an old Baty which reads in 0.0001" at 0.1" per turn which has a second small dial for up to 0.5" total travel.
      test indicator?

      Is that the true range on the indicator?
      yes, at least with all the ones I've had apart, inherent in the design. They are usually a lever of some sort or another whose range is limited by the inside space of the indicator. On the better ones there often is a rev counter.

      You don't really use a test indicator to measure, more to compare - work to a gauge block stack, one end of the vise jaw to the other, one side of the work in the 4 jaw to the other etc. As the arm comes away from straight, error is introduced so there'd be little point in trying to measure any distance with a test indicator. When you need to measure, use a dial indicator.
      .

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      • #4
        Yours probably only has .008 inch range.
        I have one with a rev counter it has a range of +- 0.030 resolution of 0.0001

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        • #5
          0.008" is plenty of range.
          I have one 1um test indicator (or dial comparator) that has +-0.04mm or +-0.0016mm range.

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          • #6
            I beg your pardon, I tend to call both types, plunger and lever, dti's. My lever type Mitutoyo's are two variations, one goes 30-0-30 in thousandths of an inch with a switch for direction and the other 15-0-15 in half thousandths of an inch. Of course these figures cannot be exact because of the sine rule.
            A Verdict lever indicator has an option of a teardrop shaped tip which compensates for the errors over a greater swing.

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            • #7
              Originally posted by old mart View Post
              A Verdict lever indicator has an option of a teardrop shaped tip which compensates for the errors over a greater swing.
              I've got one of those, a neat feature (can't say I've exactly needed it, but neat nonetheless!)
              .

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              • #8
                Originally posted by old mart View Post
                ...I beg your pardon, I tend to call both types, plunger and lever, dti's...
                They are really very different--using the wrong term will cause confusion in some situations...

                ...Of course these figures cannot be exact because of the sine rule...
                And 99 per cent of the time it doesn't matter. A DTI is most often used for comparing two points--like when you
                tram in a vise on a mill--or dialing in a piece of stock on a lathe. In both cases the actual distance measured
                doesn't matter; you simply want the dial to read as close to zero as possible...
                Keith
                __________________________
                Just one project too many--that's what finally got him...

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                • #9
                  I find the lever is far superior for trueing work in a four jaw lathe chuck, for instance, although I wouldn't use a tenths resolution one for that.

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                  • #10
                    That tenths reading indicator with only .008 travel does sound pretty specific. Any chance of a direct link to the listing?

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                    • #11
                      http://www.starrett.com/metrology/product-detail/3908A

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                      • #12
                        Thanks for the link.

                        A quick check around shows me that DTI's that are graduated in actual 10ths instead of half thou increments are not much different than the .008 of that Starret indicator. The other common total range is .01. So just two thou more than the Starret's .008. And it seems like all the actual tenths range instruments are in that same amount of total movement.

                        The half thou graduation versions seem to all have .03 total range and the one thou graduation versions are pretty well all .06

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                        • #13
                          Originally posted by Captain K View Post
                          I see dial test indicators the read to tenths but only have .008" range. Is that the true range on the indicator? Or is it just the range of the dial ie. needle can make multiple turns but there is no rev. counter?
                          Do you need a tenth-reading with more range? Compac makes a few models with .024 range.

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                          • #14
                            I'm not sure I need a tenths indicator at all, more a curiosity question. Seems like it would be hard to use an indicator with only .008" total lrange

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                            • #15
                              Originally posted by Captain K View Post
                              I'm not sure I need a tenths indicator at all, more a curiosity question. Seems like it would be hard to use an indicator with only .008" total lrange
                              Actually .008 is a *lot* compared to a tenth. There's all kinds of room in there. I think the limit on range is how much the manufacturer can actually guarantee accurate. It may move further but it wouldn't be accurate.

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