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Thread: Hollow Draw Bar

  1. #1
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    Default Hollow Draw Bar

    I'm making a hollow draw bar for locking my MT4-ER40 collet chuck into my Hercus 260 spindle bore. I'm planning to use NB15 galvanised water pipe which has an OD of 21.3mm and an ID of 16.1mm. To avoid weakening the gal pipe too much I'm planning on using 1mm thread pitch. The Sketchup drawing shows what I'm planning.

    The collet chuck is mounted in the 4-jaw and I've dialled it in to about 0.01mm runout at the far end. I've cleaned up the inside and outside of the short parallel section on the end. I had no problems doing that with light cuts.

    Do you guys think that setup is rigid enough for single pointing the internal thread?
    Attached Images Attached Images
    Chris

  2. #2
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    Default

    If I understand correctly you are going to re cut a thread (1.0 thread pitch) into your ER40 collet chuck. With not to heavy of cuts the set up should be rigid enough, the arbor of the collet chuck isn't going to be soft though. I don't understand though why you want to make the drawbar hollow, but thats your choice. Another way to do this still with your hollow drawbar is to leave the factory thread in the drawbar end of the collet chuck and weld a short piece of bolt into the end of your drawbar to suit the collet chuck.
    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  3. #3
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    Default

    Chris, use your fixed steady so you dont get a chattered thread.

    cheers, shed

  4. #4
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    Default

    Quote Originally Posted by steran50 View Post
    I don't understand though why you want to make the drawbar hollow, but thats your choice.
    Thanks Stewart. A hollow drawbar will allow me to hold long stock in my ER collets. Currently I'm limited to the depth of the collet chuck.
    Chris

  5. #5
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    If you have a fixed steady, I'd suggest using that. While you may not need it, after the part has moved is too late to think about putting it on.

    Michael

  6. #6
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    Quote Originally Posted by shedhappens View Post
    Chris, use your fixed steady..
    Thanks John. That's the reason I originally made a truing cut on the outside of the MT shank's end. But while looking at the setup I thought the fixed steady would interfere with carriage. I'll have another look. Might just need a bit more extension on the threading tool.
    Chris

  7. #7
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    Default

    I would not even attempt it without a Steady. This is a shank for a my Wohlhaupter set up for boring prior to screw cutting.

    Fixed Steady.JPG

  8. #8
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    Why don't you just buy a chuck that screws onto the spindle?
    Then you could run 25 mm through the spindle.

  9. #9
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    Default It fits!

    There's plenty of room for the fixed steady. What a goose I am. Shows how often I use the steady!

    Quote Originally Posted by pipeclay View Post
    Why don't you just buy a chuck that screws onto the spindle?
    I'd love to Peter. I keep checking Mal's website for ER40 chucks that fit the Hercus 260 spindle but he doesn't have them. I believe you make them for him? If so, any plans to supply Mal with screw-on ER40 collet chucks?
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    Chris

  10. #10
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    I have semi finished ones in the fridge.

  11. #11
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    Keep me posted.
    Chris

  12. #12
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    If I finish machine them I can guarantee how true it will run on your machine, if you are prepared to machine your current collet chuck and draw tube you would have no trouble finish machine this.

  13. #13
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    I'm happy to finish the taper.

    Edit: I guess I would need to cut the thread for the nut too?
    Chris

  14. #14
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    I think you may not be happy with the result, single pointing galvanized water pipe.
    I have tried this on a number of occasions and I have never been satisfied with the result.
    If you can get black pipe, I have found it machines much better.
    Regards
    Bradford

  15. #15
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    G'day Chris,
    I got one of Peter's screw on ER40 chucks for my 260, just needed to machine the taper and its dead on. Best thing since sliced bread, I wouldn't mess around with the draw tube.
    Cheers,
    Greg.

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