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  1. #1
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    Default Threaded handles for machinist clamps

    So, I have a pair of unfinished clamps without the threaded handles, and am trying to quickly finish them. Can't be bothered turning down stock, threading, knurning, and cross drilling.
    (like a million apprentices have for centuries )



    Threads are 3/8 Whitworth. Toolmaker suggested socket head screws, and weld/braze a rod as handle on to the top. Alas, I couldn't find cheap high tensile screws with decent thread length.

    So, grabbed some cheap bolts from the "red hammer warehouse":
    IMG_2806.jpg


    The "expanding" thread handle is easy. I just machine the end to fit the pocket:
    IMG_2994.jpgIMG_2996.jpgIMG_2997.jpg



    The "tightening" handle requires some thought, though.

    Needs a sleeve to clear the square lock under the bolt's dome head.
    Or maybe bodgy some washers and weld the whole lot to a rod for the cranking handle?

  2. #2
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    6,439

    Default

    Hi Nigel,

    I would have turned off the square under the head first !
    Best Regards:
    Baron J.

  3. #3
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Nigel,

    I would have turned off the square under the head first !

    Fair enough. I was thinking that might weaken the bolt head,

    ...but it saved time looking for washers, so:
    IMG_3001.jpg IMG_3002.jpg


    Then, ground some slots in the head, found some old 1/4" rod, bent a crank on one end:
    IMG_3003.jpg IMG_3004.jpg


    and did some welding:
    IMG_3005.jpg IMG_3006.jpg


    Sadly, on one of them I undercut the rod, and trying to build it up again failed.
    Will have to find some more rod tomorrow

  4. #4
    Join Date
    Sep 2008
    Location
    Riddells Creek, Vic.
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    831

    Default

    That type of handle will really restrict the usability of the clamp.

  5. #5
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    Default

    Restrict? Yes, they will get in the way sometimes, but cheap and fast sometimes wins out.
    (often, for me)



    The other way they restrict is not clamping below about 30mm:
    IMG_3007.jpg
    because the thread on the expanding handle doesn't go far enough.

    For now, I die cut its thread 10 or 15mm longer:
    IMG_3009.jpg




    Eventually, I might make some better handles from booker (all thread) rod,
    with machined/knurled/cross-drilled heads.

    I would have gone that way initially, except that all the threaded rod I found was rubbish.
    Either soft mild steel which is soooo loose that it would strip at first clamping,
    or stainless that was better, but I don't trust to not gall or fail under stress.

  6. #6
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
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    Default

    Stainless probably not too much of a problem if the clamp jaws are not stainless as well. I agree that hi tensile thread would be better though, as would a much finer thread. Some of the model Engineer threads - either 32 or 40 tpi would give lots of clamping power.

  7. #7
    Join Date
    Apr 2012
    Location
    Healesville
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    2,129

    Default

    Quote Originally Posted by nigelpearson View Post

    because the thread on the expanding handle doesn't go far enough.

    For now, I die cut its thread 10 or 15mm longer:
    Nigel coach bolts have a rolled thread so the unthreaded section will be too small in dia to get a decent thread cut there.....

  8. #8
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    Aug 2019
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    Quote Originally Posted by shedhappens View Post
    Nigel coach bolts have a rolled thread so the unthreaded section will be too small in dia to get a decent thread cut there.....
    Indeed. I noticed that when cutting, so only did about half of the depth through the clamp blocks – to still provide some clamping strength.


    Their steel is fairly nasty rubbish. Maybe from the bright galvanising?

    I doubt they will last long, but I'm hoping soft thread in the handles will spare the threads in the clamp blocks.

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