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Thread: COAXIAL INDICATOR

  1. #13
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    I guess I don't see (no pun intended) the big deal about using a standard DTI to center a bore on a part. If the bore is already machined you only need to indicate three of the sides. If you want to indicate all four directions a inspection mirror makes the job very simple.

    A mirror similar to this is invaluable to a machinist/die maker; KD Tools 2108 - Rect Mirror 2-1/8"X3-1/2" 15-1/4 Wand



  2. #14
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    Default coaxial indicator with short body?

    Anyone know where to get these? I am using a cnc swiss lathe with small Z travel.



  3. #15
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    J&L / MSC
    Blake Co-axial indicator - they have cheaper knockoffs, but you get what you pay for here.



  4. #16
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    Oops - don't know that I have ever seen a short body version.
    You may be stuck with standard indicators for a swiss machine.



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    Default Re: COAXIAL INDICATOR

    Quote Originally Posted by wildwestpat View Post
    Hi Folks


    That table shows that the shorter arm gives less sensitivity i.e. less deflection as seen per divisionon the inbuilt indicator dial. The longer the probe the greater the deflection of the pointer but the accuracy is for all intents and purposes independent of probe length as the device is being set for minimum flap of the pointer which is why it is best to use the longest one that is convenient for the job.

    If you want to measure the concentricity then use a DTI corrected for approach angle - a very tedious process and best done in the tool room. The co-axial indicators are intended for quick and easy centring on the machine with acuracy and speed. These instruments are robust and can take a lot of punishment. Hope this clarifys the use of the table.

    Regards - Pat
    Surely, the shorter arm give MORE sensitivity-it is the long arm that will give less deflection on the indicator.

    Andy


  6. #18
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    Default Re: COAXIAL INDICATOR

    Finally someone got the geometry concept correct. Thank you awander. A longer arm decreases sensitivity, and shorter arm increases it. It seems lost on most the main advantage to a coaxial indicator is you can stand on one place and indicate a hole. NSEand W, without bending and moving to see the indicator. Yes, you can do the 3 point method; left, right, and front. But you still have to bend left and right to view the dial with a conventional DTI. And if the hole is not quite round, you'll have more error than if you work 4 points.



  7. #19
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    Default Re: COAXIAL INDICATOR

    hello guys, hello vette, wow, a thread about coax

    Quote Originally Posted by sld4121 View Post
    The shorter the arm, the more accurate the results yes. My "cheaper" version came with a conversion factor of sorts to assist with that
    Quote Originally Posted by wildwestpat View Post
    That table shows that the shorter arm gives less sensitivity i.e. less deflection as seen per divisionon the inbuilt indicator dial
    please, can someone share such a table ? thank you





    so far, i have used only haimer centro :

    ... when the indicator moves a full revolution on the dial, the palpator moves with circa 0.85 degrees, regardless of palpator length

    ... if i use the straight palpator from haimer, and the palpator position is :
    ...... pretty paralel to centro axis, then the dial will show a value pretty close to the real value
    ...... tilted, then the dial will still show a value pretty close to the real value, but affected by a deviation caused by the tilted angle; the more you tilt the palpator, error increases ( obviously, you can not center a hole if the palpator is tilted 90 degrees, but also, small tilt angles do not input a huge error; mathematically, there is a threshold angle, until which this error is manifested after many digits, thus beyond 0.001, thus it's effect occurs at a small scale, so it can be ignored in reality )

    ... if i use longer palpators ( homemade, straight / curved / double curved, etc ), then the dial will show a value affected not only by the tilt angle, but also by the ratio between the " length of the custom palpator" and the ''length of haimer palpator = reference length"; for example, if the "longer palpator" is paralel to the centro axis ( tilt angle = 0 ), and it is twice longer then the "haimer palpator = reference length" , and the real value is 0.4, then the dial will indicate 0.2, thus only half of 0.4

    about this " reference length ", pls check dimensions from attached image; image is not at real scale, but pls observe that those dimensions are pretty equal; if a "palpator length" = "reference length ± a bit", then displayed value is pretty close to real value / kindly

    Attached Thumbnails Attached Thumbnails COAXIAL INDICATOR-00-png   COAXIAL INDICATOR-01-jpg  
    Last edited by deadlykitten; 01-18-2019 at 10:12 AM.
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg


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