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Forrest's Dial Indicator Article

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  • Forrest's Dial Indicator Article

    I just got my issue yesterday, and read with interest the article on usind DIs. One question though. When setting one up to measure table travel for instance...How do you ensure that the DI is perfectly perpendicular to the table? I am using one of the articulated arm type mag bases. The cosine error thing has me a bit confused. Thanks.
    Arbo & Thor (The Junkyard Dog)

  • #2
    calibrated eyeball.

    if it's straight enough if you can't tell its crooked, then the cosine error is to small to care.


    • #3
      The cosine of 1 degree is 0.999847 so the max error for a 2" DI (at 2" of travel) would about 3 tenths. A one inch DI would be about 1.5 tenths. Good enough for government work.

      If you need better than that, install a really good DRO. And verify that it is parallel to the ways. Mucho dollars. And send me your unused DI. I will give it a good home.

      Basicially I eyeball the DI's shaft with one of the elements of the machine that is at the desired angle, like the lathe ways or the slots on a mill table. A square can be used to good effect also.

      Oh, and use an actual DI, the kind with the linear shaft, not a dial test indicator with a rotating arm. The rotating arms will get into errors when rotated very small distances off the perpindicular position. They are primarily for centering and comparison measurements and their actual measurements can not be trusted for more than 5 or 10 thousanths.

      Paul A.

      [This message has been edited by Paul Alciatore (edited 01-07-2005).]
      Paul A.

      Make it fit.
      You can't win and there is a penalty for trying!


      • #4

        .0003 over 2" for one degree makes me feel alot better. I have forgotten more about trig than I will probably ever learn again. When in high school, I aced trig, calculus, advanced math, and all that stuff. I loved it! But now, after not using it for many years, I wish I had remembered more. Thanks alot!
        Arbo & Thor (The Junkyard Dog)


        • #5
          This sounds great!
          Can someone email a copy of this!?
          please visit my webpage:


          • #6
            No. No, NO! NO! NO! Bad Hoser!

            Go out and buy the magazine so Neil can feed his starving dog - no, his dog is not starving, but by asking for someone to email this COPYRIGHTED article out of a magazine you are stealing the food out of Neil and his crews mouths - so stop trying to steal and play nice like the rest of us.

            [This message has been edited by Thrud (edited 01-08-2005).]


            • #7
              Sorry,Thrud you are right
              (hanging my head in shame)
              ps I will subscribe!!
              please visit my webpage:


              • #8
                Holy Crap Batman!That reminds me,I need to renew my subscription!!!
                I just need one more tool,just one!


                • #9
                  As a complete novice to machining, I’ve found all of Forrest Addy’s latest articles immensely helpful. BTW, can anyone direct me to a site or image of a Starrett No. 198 or a Mitutoyo 95-158, as mentioned in the latest article. I did search but no results. Just like to know what they look like.



                  • #10
                    The Starret #198 is pictured in the article but the image is a bit on the small side.

                    It's in the back of the group picture where all the indicators are spead on the granite flat. There's the Starrett #198 wood box with the lid off with the indicator and attachments either displayed on the box or immediately in front.

                    I don't think Starret still sells the #198 but there are millions are out there someplace. Every first year apprentice machinist and tool maker from 1928 to the present day got one from his family for Christmas or his birthday.

                    [This message has been edited by Forrest Addy (edited 01-09-2005).]


                    • #11
                      Starrett never did make a No. 198 Test Indicator. They did, and still do make a No. 196 though;

                      BTW, I don't know if Federal ever did make a version, but Lufkin made a No.399 that, like most Lufkin tools, blows the Starrett away. It has an end reading hole attachment that does away with that funky double ended swivel attachment Starrett has.

                      I also have a Scherr-Tumico version that is made in the UK that is very nice.

                      [This message has been edited by JCHannum (edited 01-09-2005).]
                      Jim H.