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Thread: Universal Grinder Fine Feed Adjuster

  1. #21
    Supporting Member jjr2001's Avatar
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    Jun 2016
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    Hello ncollar, Actually the knob is graduated. Post 17 shows the knob detail with the long lines being .001 and the half lines being .0005.
    It does not show up that well in the thumbnail but if the thumb nail is clicked to large size the graduations shows up.
    No calculations required.

    Thanks for checking in.

    Cheers, JR

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  2. #22
    Supporting Member mklotz's Avatar
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    Quote Originally Posted by ncollar View Post
    All that math is alright if that is the way you do it. I would put a mark on the face of the knob with a marker and a DTI, make one revolution of knob, then figure out how many lines you would like to put on the dial. If one rev is .0010 then 10 lines would be .0001 per line. No math to error.
    The problem with that approach is that if you want one full revolution to be some "nice" number (e.g. 0.010) rather than some inconvenient increment, you must take account of the mathematics of the design. (Besides, you'll never learn any math if you avoid opportunities to use it in practical problems.)

    The brass wedge will rise by:

    P * tan(A)

    for every revolution of the screw driving the steel wedge. Here

    P = screw pitch = 1/tpi
    A = wedge angle

    Let H = desired rise for every revolution of adjusting screw. Then we can solve for the required wedge angle...

    H = P * tan(A)

    A = arctan (H/P)

    As an example, for ten thousandths rise per revolution of an 18 tpi screw, we have...

    H = 0.010
    P = 1/18

    A = arctan (0.18) = 10.2 deg
    Regards, Marv

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  3. #23
    Supporting Member ncollar's Avatar
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    Math and history was my best subjects in school. I forgot so much of that it would be like going back to school, but once you learn to ride a bicycle you never forget how to. I guess I just do it the easiest way to me, the KISS theory.
    Merry Christmas

  4. #24
    Supporting Member jjr2001's Avatar
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    Thanks for the detailed math explanation to the problem Marv. I can use that on my next wedge lift system.

    I must admit that I used the DTI method to get a "close" solution. I just looked at my setup and found that
    I have a .001" error in a full turn of the knob. One line is close to .001 but just a bit short. I usually work to .001"
    for most of my builds and that is more than I usually need..However I always spend considerable time
    fitting up the parts. So time could be saved with using the proper math for the solution.

    Thanks again and Cheers, JR

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