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Thread: Centering my 4 jaw chuck

  1. #31
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    May 2009
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    Quote Originally Posted by brian Rupnow View Post
    (snip) Paul, you're not raining on my parade at all---but having the horizontal stem of the indicator on the same horizontal centerline as the lathe's main axis is the easiest way to ensure that the axis of the D I intersects the main axis of the lathe.
    There is no problem with the axes intersecting, if that is what you want.
    Repeating Mr. Alciatore, it is not necessary. The indicator reads relative motion.
    If you shift the work using the 3 & 9 o'clock jaws, then the indicator is best placed in one of their quadrants.
    Rolling the chuck so that 3 & 9 are now 6 & 12, but not moving the indicator will reveal the same thing as having the indicator absolutely dead nuts within one micron of the horizontal axis and the indicator tip plane perpendicular to that axis within one micron.
    Sine error does not matter, until the indicator jams.

  2. #32
    Join Date
    May 2015
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    Somerset UK
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    Remember, when you are using a dti for checking runout, make sure it is held in such a manner that it can be knocked aside easily. Holding rigidly is asking for trouble.
    I personally prefer to use a lever type, making sure not to stress the lever sideways.
    For initial rough aligning, just use the lathe tool and mk 1 eyeball before setting up the dti.
    If, say for example, the work is square, then only allow the tip of the dti to touch, you don't want the tip to follow the profile like a cam follower on a cam.

  3. #33
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    Mar 2001
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    LA, CA, USA
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    Quote Originally Posted by old mart View Post
    If, say for example, the work is square, then only allow the tip of the dti to touch, you don't want the tip to follow the profile like a cam follower on a cam.
    Or you can make a "flapper" like this...

    http://www.homemadetools.net/forum/c...al-stock-27183

    to protect the DI.
    Regards, Marv

    Home Shop Freeware - Tools for People Who Build Things
    http://www.myvirtualnetwork.com/mklotz

  4. #34
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    May 2015
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    Another reason I avoid plunger dti's used horizontally is that the tiny bit of friction caused by the weight of the plunger can give unpredictable readings. The high point reading can be unreliable.

  5. #35
    Join Date
    Sep 2006
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    Big Prairie Mi.
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    Marv's 'flapper is similar to what I use for centering, they work well for pretty much any stock. Before I used it, I did break a lever indicator, fortunately it was a cheap HF so no big deal and was a cheap lesson.

  6. #36
    Join Date
    Dec 2007
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    Montezuma, IA
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    I mark out the hole location and use a prick punch on it's center, then use a sharp dead center in the tailstock to rough align the hole location in the four jaw chuck. Trade out the dead center for a chuck and the long pointed bar set in the punch mark along with the dial indicator make for quicker work.
    David Kaiser
    “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
    ― Robert A. Heinlein

  7. #37
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    May 2015
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    I sometimes use the dead centre method, it is very good and gets you within a few thou. I have also used that method for holding work on a faceplate before clamping up.

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