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  • thread milling

    Goodmorning gentlemen,

    Looking for info about building a thread- milling attachment for a small,(9") lathe. I would like to hand turn the lathe spindle and have a motorized cutter mill the thread right up to a shoulder. It almost seems that this could be done with a slowed down toolpost grinder? Thoughts?
    thanks
    hms50
    hms

  • #2
    A guy called J.A. Radford did this and described the method in an article in Model Engineer in the spring of '72. Volume 138 issues 3437 and 3438.
    The same article had been reprinted in a book called Improvement and Accessories for your Lathe again by J.A. Radford ISBN No 1 85761 105 5 published by TEE Publishing.
    http://www.fotec.co.uk/mehs/tee/index.html
    he built a complete tool with it's own motor drive and worm and wheel reduction to get the milling cutter speed down low enough.
    A very good article. The book is well worth buying as that attachment is only one of 20 described in the book.

    John S.
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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    • #3
      John, thanks for the info! I just checked the link and ordered the book. I appreciate your help and advice.

      hms50
      hms

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      • #4
        I have considered this for the big ugly threads on my lathe. My thoughts went the other direction - 60* solid carbide burr and 28,000 rpm trimming router. The trimmers are cheap (in a relative fashion) and I figured I didn't have one in the old tool pile anyway...

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        • #5
          Is it possible to use a lathe milling attachment for thread milling? ie by laying it over so both spindles are in the same axis?

          You may be interested in a thread milling device I have that was made for thread milling in a vertical milling machine and it is very simple. This was made in the toolroom for machining threads into plastic injection moulded bottle cap dies.Not sure how common it is. We had to mill unusual threads of say 2 1/2 turns onto a toolsteel shaft of say 1" dia. This formed the internal thread of the plastic bottle cap. The thread could be a radius or type of butress thread or any of the other strange threads found on bottles. The cutting tool was a single point HSS tool, ground to the thread form and held in a bar similar to a lathe boring bar, but held in the milling spindle collet.
          The thread milling device is straight forward - a solid steel "spindle" approx. dia. 100mm x 200mm long, the "top" end is fitted with an adaptor plate for mounting different work pieces, the "lower" end recessed to hold a threaded "master". The spindle fits into a heavy-walled sleeve, which is approx. 200mm long, with a square base plate on it's lower end. This plate allows the device to be clamped to the mill table, and also locates the other half of the thread "master". The threaded master is just a thread and nut, cut to whatever pitch is required on the workpiece. Therefore, when the spindle is rotated in the sleeve, it also moves up or down in the sleeve at whatever pitch the master thread has.
          The adaptor plate on top of the spindle has a handle to allow it to be turned by hand. The workpiece is mounted on this adaptor plate. The spindle is turned the required number of turns, slowly, by hand, as the rotating single point cutter cuts the thread.
          It works well. It is easy to make up different "thread masters" for other pitches.
          Any other methods of doing this out there?
          If you have a milling machine, this method is probably easier than making up a powered cutter for the lathe?

          [This message has been edited by Peter S (edited 05-29-2002).]

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          • #6
            Peter S:
            There actually is an attachment to mill in the lathe and it is clamped in the tool block and used like a - router! The one sold in England is almost the price of a new lathe and has a 400-4,000 rpm range. I think they use ER-16 collets in it.

            My thought is of the same thing - except I would use a carbide burr and very high rpms. using the thread pitches built into your lathe would feed the unit the proper distance and the burr would grind away. The lathe could even be "hand cranked" to do this. This is one way you could cut larger threads in a smaller lathe shuch as a Sherline. Those 4 tpi threads would look nice and "shiney". And we all know "shiney" is a good thing. Or, at least us crows do!

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            • #7
              Peter,
              Wow! what a neat approach to the problem! I'd like to try this on my Bridgeport. Any way to get photos or a sketch? It sure would make it easier to construct. How do you clamp the workpiece?
              Thanks,
              Hugh
              hms

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              • #8
                Hugh,
                Yes, it is very simple and clever. Easy to make. Unfortunately I can't take any credit for it.
                I can take a photo, but it will take a while to develop and send. I'm still living in the camera dark ages. A sketch is possible, maybe scanned, or???
                Clamping workpiece? The adaptor plate on the top is probably about 150mm (6") dia, so there is room to tap holes for clamps or hold-down straps. The pieces we were thread milling were kind of unusual, they had a large flange which was easy to clamp to the adaptor plate. The adaptor plate was actually machined specially to locate them.

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                • #9
                  Peter,
                  Super! A scanned sketch would be great! Could you e-mail it to me as an attachment? I'll be on summer vacation in a few weeks and this would be a great project.
                  Thanks
                  Hugh
                  hms

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