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Thread: Half Dead Centers

  1. #11
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    Quote Originally Posted by danlb View Post
    My solution was simple and does not require any permanent changes. Each of these delrin spacers has a rare earth magnet pressed into a recess.

    Two different MT mounts, both too short. Two spacers that snick into place, giving exactly the right length.

    That's a good idea. A spacer held in place with a magnet makes it easy to use on the next taper that may have the same length issue. I don't use two tapers at the same time.

    JL...............

  2. #12
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    I have a smaller lathe that uses the same taper, so using the magnet allows me to remove the spacer when I want to use that live center in the smaller lathe. While it's in the smaller lathe the spacer sticks to the body of the tailstock.

    Dan
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

  3. #13
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    Quote Originally Posted by JoeLee View Post
    Here is a picture of the half dead next to one of my regular centers. The both look the same as far as length etc.

    Here is a picture showing how much of the end of my regular center protrudes from the end of an adapter bushing. The end of the taper protrudes about .146 from the end of the adapter.

    Here is a picture of the half dead center in the adapter. The end of the taper protrudes about .028 when seated.

    Best I can measure at the end of the taper..... the regular center measures .792 and the half measure about .801. Does that sound about right for all you math guys??
    .009 difference on the taper dia. equal about .118 difference in where it seats.

    JL.............
    If you look, you will see that the half center is likely to be really shorter if measured from the "gauge line" of the taper, the point intended to be at the front of the quill, to the end. That's obvious from the seated positions.

    So actually that is a "short taper". Put something on the back and get on with work. Magnet and delrin seems good, with fewer issues implementing it, but there are other solutions as well.
    1601

    Keep eye on ball.
    Hashim Khan

  4. #14
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    Quote Originally Posted by danlb View Post
    My solution was simple and does not require any permanent changes. Each of these delrin spacers has a rare earth magnet pressed into a recess.

    Two different MT mounts, both too short. Two spacers that snick into place, giving exactly the right length.

    Winner winner, chicken dinner!

  5. #15
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    Spacer with a magnet is a good idea, indeed. I just wonder what you used to attach it to Delrin, Dan. I'd, probably, used something more "glue-friendy" for the spacer.

  6. #16
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    Quote Originally Posted by MichaelP View Post
    Spacer with a magnet is a good idea, indeed. I just wonder what you used to attach it to Delrin, Dan. I'd, probably, used something more "glue-friendy" for the spacer.
    Probably a good press fit would do. The only issue with this that I see is that the magnets are probably too thick, unless they come in different thicknesses.
    I only need about an 1/8". Most of those small magnets I've seen are about 1/4" in thickness.

    JL.............
    Last edited by JoeLee; 02-13-2018 at 10:48 AM.

  7. #17
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    If the plug is thicker than needed it will only reduce the quill movement slightly before extracting. The magnet in plastic is good, but I would use brass and have the magnet slightly under flush, so the brittle magnet is protected from being crushed.
    If the centre is fitted into a parallel shank holder, it would be easy to drill the base to fit an extension assuming the rear is not as hard as the tip. You could probably hold the centre in a three jaw chuck well enough to drill, there is normally a hole from when it was originally ground.

  8. #18
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    I wasn't nearly as hi-tech with the shank on my tailstock chuck. I just built it up on the end with some mig weld.
    Brian Rupnow

  9. #19
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    drill and tap the end for a set screw, then you can adjust the ejection point to your liking

  10. #20
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    Quote Originally Posted by MichaelP View Post
    Spacer with a magnet is a good idea, indeed. I just wonder what you used to attach it to Delrin, Dan. I'd, probably, used something more "glue-friendy" for the spacer.
    The magnets are very thin, about 10 to the inch (probably 2mm). To hold it in I simply undercut the edge of the pocket and pressed the disk into the pocket. The tool used to undercut was a mico100 inside threading tool.

    In reply to Joe's post, the magnets were probably 10mm x 2mm from banggood . $8 shipped for 100 of them.

    ( Take your pick; https://www.banggood.com/buy/neodymium-magnets.html )

    The magnet does not need to be real strong. It just makes sure that the spacer comes out with the tool.

    Dan
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

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