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DTI Noob

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  • DTI Noob

    I use my mike (It's german made. It seems my great-grandfather was an old South Mend Lathe And No Mill machinist and My grandfather was more a woodworker but eclectic hobbies and precision woodworking led him to keep/buy a few tools. So I have an Indian vernier that is impossible to read and is made out of stamped steel, a German mike, a depth gauge mike, and a Starrett .001 1-inch DI. Then I have another pair of stamped steel calips and some rules.
    The thing is still one thousandth graduation, who knows what accuracy. I guess the only real differnce is that I can square my milling vise with it, and maybe do a bit more runout measuring. What exactly do you mean by swiviling the point/lever? Is the range of measurement much smaller than the range of movement? What exactly can you do on a DTI that you cant on a DI and is it really useful for someone with a very short budget>

  • #2
    you are correct the range of movement is usually much less. it also has a negative range as well. My Mitutoyo DTI has a range of -.004" to +.004" and has .0001" graduations. Thus I have 10 times the resolution of a standard DI , but less than 1/10 the range .


    take a look at the DTI on this page.
    http://littlemachineshop.com/product...ory=1310310429

    see how the lever (the part with the ball on the end) is parallel to the body? It doesn't always need to be parallel if you push on it you can make it perpendicular to the body (or any other angle you want).
    -Dan S.
    dans-hobbies.com

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    • #3
      My view is that a DTI is more rugged and (typically) much higher resolution with the added bene of having a finger to reach inside bores and such. For comparative measurements like tramming or dialing a 4 jaw, it just doesn't get any easier. Plus the "finger" can be oriented for easy viewing of the dial and/or easy "ramping" over broken surfaces (like t-slots). They also (usually) have nice dovetail mounts on the better DTIs (excludes LastWord which has proprietary mounts). That makes them easily adapted to many different mounting fixtures much easier than trying to find the right combo "snug" or the like...

      They are also much cheaper than comparable accuracy/resolution DIs. However, their primary accuracy boon is pretty much just comparative due to the "cosine error" caused by the arc of the "finger".

      However, a DI with the proper attachments can do most anything a DTI can, though with generally much less resolution. For instance, I have a Starrett plunger back DI with full set of attachments including a rocker/finger thingy for getting into a bore. But this is MUCH more cumbersome and fiddly than grabbing a DTI.

      I use a DTI far FAR more often than a DI. I reach for the DI only when I want accurate quantitative measurements. And that generally means on the surface plate, or maybe clamped to the bed of a lathe (before I got DRO). A DI will also have a much larger range, so if you need more than about 0.050 (up to a max of something like 0.100 depending on brand and resolution) range, you have to move to a DI.
      Russ
      Master Floor Sweeper

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      • #4
        OK. I am sure you still want a DI for rough centering and stuff but a DTI seems good. Worth the 50 bucks EBAY anyway.

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        • #5
          Originally posted by ikrase
          OK. I am sure you still want a DI for rough centering and stuff but a DTI seems good. Worth the 50 bucks EBAY anyway.

          Just make sure its a good brand, a DTI is one of the tools not to skimp on in my opinion.
          -Dan S.
          dans-hobbies.com

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