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  1. #1
    Join Date
    Mar 2017
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    Default Hercus collet draw tube

    I picked up a genuine Hercus 3C collet set at the Bendigo swap meet last weekend. A nice complete set with the storage stand and all. After cleaning it up I have found the thread in the collet end of the draw bar to be in poor condition. Probably not so unusual. I thought I might make a new one. A bit of research suggested the internal thread (collet end) is an odd thread of 0.635" x 26TPI, so that will have to be cut in the lathe. The external thread at the other end is 3/4" x 24TPI, which I can get a die for, but will probably also cut that on the lathe (maybe use the die to tidy it up).

    Anyway, my question: can someone direct me to a supplier of the tube stock?

    The tube is a thick walled tube, or hollow bar, 19mm OD and 13.75mm ID. This gives a wall thickness of 2.6mm in round numbers. Getting 19mm OD tube is OK, but the thickest wall tube I can find is 1.6mm - which is just too small for the internal thread (and leaves a pretty thin wall on the external thread). I believe the original tube was mild steel.

    I'm in Melbourne. Happy to buy a longer length if need be (maybe make a few tubes for others, or just cut off a length if someone else wants to share the 'experience').

    You may also have some alternative/better suggestions to solve my problem.

    Thanks in advance, Tony.

    PS. the internal thread of 0.635" x 26TPI is mighty close to 5/8 x 26TPI BSB (for which taps are available), but not quite. Some research suggests a tap of this size may end up with some very tight collets.

  2. #2
    Join Date
    Nov 2008
    Location
    Perth WA
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    65
    Posts
    5,911

    Default

    Have a look here Tony - Round Tube 4130 Chrome Moly Stocklist Information

    Is the thread in the draw bar restorable? Picking up the thread would probably be tricky but armed with a jeweller's loupe and a bright light along with a smallish boring bar, you might get there.

    Bob.

  3. #3
    Join Date
    Mar 2017
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    Melbourne
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    Default

    Quote Originally Posted by Anorak Bob View Post
    Have a look here Tony - Round Tube 4130 Chrome Moly Stocklist Information

    Is the thread in the draw bar restorable? Picking up the thread would probably be tricky but armed with a jeweller's loupe and a bright light along with a smallish boring bar, you might get there.

    Bob.
    That is a very handy mob to know about. Thanks. I'll give them a call and see if they can help. I wonder if they have a min order value? There is a place in Melbourne I get silver steel from - min order $200.

    Yes, will try and pick up the existing thread. Tricky operation. Some of the thread is actually missing (broken off), so that's why I thought I'd have a go at making one.

    Thanks again, much appreciated. Cheers, Tony

    Sent from my SM-G955F using Tapatalk

  4. #4
    Join Date
    Jun 2013
    Location
    Tasmania
    Posts
    202

    Default

    Could you just bore out the thread and then silver solder in a bushing turned to size. Then bore your ID and re-cut the thread?

    Might be easier and cheaper than buying a new piece of tube.

    Otherwise you could just dock off the damaged thread bit, silver solder in a length of steel, drill/bore and then face to length and recut your internal threads.

    Nothing to lose trying.

  5. #5
    Join Date
    Mar 2017
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    Default

    Good suggestion. I was also contemplating drilling out a solid bar - if I couldn't buy a tube of the right dimensions. The tube is 15" long, which presents it's own challenges to drill out, say 13mm. The bushing idea would be quicker and easier.
    I also thought that if I could buy the right sized tube, I could make a few, as others may interested in one. Maybe....
    Cheers, Tony

    Sent from my SM-G955F using Tapatalk

  6. #6
    Join Date
    Oct 2011
    Location
    Central Coast, NSW
    Posts
    1,038

    Default

    HI,

    You could buy one of these from AMWH:

    Hercus 260 ER32 collet chuck

    I'm thinking of getting one as I can't cut imperial threads on my Hercus 260 without a transposing gearset which costs more and I may only use once.

    Ben.

  7. #7
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    1,678

    Default

    I'd love one of those in ER40. Like Ben, I want one off the shelf. Note that they are listed as out of stock.
    Chris

  8. #8
    Join Date
    Mar 2017
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    Melbourne
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    Default

    Thanks for the suggestion Ben. Really like the idea of using the ER collet system on the Hercus. The device you suggested does away with the need for a draw bar, and will allow a slightly larger diameter of work piece to extend through the collet chuck and into the spindle. All good.
    Totally unrelated to this thread/topic, one started up about collets and chucks here What is the Morse taper size ? . Interesting, and now related, discussion on these ER spindle nose mounted chucks. The group there favoured making your own - partly for the fun and challenge of the exercise, and partly because making it on your own machine will help minimise run out. If you can't cut the spindle thread on your machine, perhaps you could ask someone to do that on their machine - then you machine the ER collet holding part on your machine, which should still give you the benefit of minimising run out (despite the thread being cut on another machine). Just a thought.
    As to my original question about re-manufacturing the original Hercus draw bar for 3C collets - this is important to me, as I have the Hercus collet set and wanted to keep my lathe as original as possible. The challenge is finding a hollow bar, of the correct inner and outer diameter. I did contact Performance Metals in NSW (suggested by Anorack Bob), but they were not so keen on small quantities and it all seemed a bit hard......the only other place I found, fortunately closer to home, was Bralco Metals (trading as Airport Metals). I have purchased a length of chrome moly steel 3/4 inch OD and 33/64 inch ID (or 19.05 OD and 12.95 ID). Perfect! Just a small matter of cutting the threads now - I reckon the internal thread will be a challenge.
    Cheers, Tony

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