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  1. #1
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    Default Two speed vice screw

    Hi,
    I was talking to Ray on the weekend about my mill vice and said I would pull it apart for him. Here is a picture of the insides, I am yet to work out how or if the brass nut is removable. The main thread is 2 tpi, the thread inside the brass nut is (roughly) 2.5tpi and allows (about) 290 degrees of rotation. The nut is spring loaded on the shaft so that it undoes first and does up last. This means as the moving jaws is tighten the shaft and nut turn together, closing the vice at 1/2" per turn. Once the work puts pressure on the movable jaw this stops the brass nut from turning. As the shaft continues to turn it is still moving forward at 1/2" per turn, it winds out of the brass nut at a rate of 0.4" per turn so the second "gear" is 0.1" per turn. Simple lol

    Hope that all makes sense and that my math is correct.

    Stuart
    Last edited by Stustoys; 10th Oct 2011 at 09:48 PM. Reason: spelling

  2. #2
    Dave J Guest

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    What a neat idea, and since you have the idea of how it works and the dimensions, I will put my order for you to make me one to suit my vice.

    Dave

  3. #3
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    Hi Stuart,

    Thanks for posting that, I can't believe how simple it is, I was expecting to see some complex clutch and multicut thread arrangement, just a nut with a fine pitch that stops turning when the jaws start to tighten.

    For those who are trying to figure out what this is all about, Stuart was using this vise on the table next to me and Josh on the weekend, and he demonstrated how it had a two speed action. Fast open and close, but automatically slowing down to a different gear ratio when the jaws started to either open or close, so you got the clamping force of a low ratio, with the opening / closing speed of a high ratio.

    Simple solution.

    Regards
    Ray

  4. #4
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    Hi Dave,
    2 tpi square thread? The best I have done is 4tpi with a turning tip lol I'd have to drive the spindle from the leadscrew and RC(?) was talking about on the weekend. Still it is a very nice looking thread.

    Quote Originally Posted by RayG View Post
    just a nut with a fine pitch that stops turning when the jaws start to tighten.
    No problem Ray, though it did take a little to get my head around what was going on. Just to clarify, the nut doesn't have a fine thread, its the difference in pitch between the threads that gives you the "fine thread". Now come put it back together lol

    Stuart

  5. #5
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    Stuart, I think I get the concept but I'm struggling a bit with the detail. Before you put it together can we have a pic of the nut? Obviously the two threads are left and right handed. And one is inside the nut and one outside? So it's a nut within a nut? Is that a spring next to the clip? It sounds so simple and ingenious I really want to get it.

  6. #6
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    bump.
    I thought it showed as a new post if a post was edited. It appears that that isnt the case.

  7. #7
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    By George I think I've got it. Diabolically clever. Thanks a lot for taking the time to photograph and explain it.

  8. #8
    Dave J Guest

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    I think you only posted that to screw us over.
    Thanks for the pictures, I had a good idea but they helped as well.

    As for editing, as you found out it wont be a new post. Some people edit there post with out saying they did, so it gets missed by everyone as they don't know and have already read that reply.
    Most forums automatically put down the bottom that it was edited, but on here you have to put it in yourself by typing in the reason for edit box.

    Dave

  9. #9
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    thanks Stuart and all the others for the replies. I will read and re-read your description until I can get my head around it too. Stuart where do I find the picture of the insides. As mine is in pieces I will photograph the parts today and post.
    And Stuart my brass nut is held in with an external circlip on the spring side of the nut.

  10. #10
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    Hey don't blame me, it had pictures and I did warn them

    Given it would seem I didn't give much of an explanation of my pictures last time, I've dug them up. Though I dont seem to have a picture of the brass part off the screw.
    Pic 1 is the starting point.
    Pic 2 screw and brass part turned one turn into nut, gape closes about 14mm on the rule, notice the black line around the screw hasnt moved in relation to the brass part.
    Pic 3 screw turned about 60 degrees into nut without the brass part rotating, Notice the black line has moved as the screw move out of the brass part
    Pic 4 screw turned about 270 degrees into nut without the brass part rotating, screw has moved about 13mm since Pic 2, the Brass part has only moved about 4mm
    Attached Images Attached Images
    Last edited by Stustoys; 2nd Jul 2019 at 11:30 PM. Reason: typo

  11. #11
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    Thanks for the pics stustoys. I can see the workings of the threads, but a bit confused about the spring. I assume the brass nut is at the end of its travel in pic 1, so does the spring hold it in this position as a default? I have tried this spring setup and I am lucky if I can get the brass nut 1/2 turn backwards on the shaft due to the spring tension.
    So by winding the brass nut to close the jaws that is the fast speed and then nipping the shaft up via the handle to lock in the work piece constitute the low gear/ speed. Does this sound like how the vice works?

  12. #12
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    Quote Originally Posted by hpa1 View Post
    I assume the brass nut is at the end of its travel in pic 1,
    Yes

    Quote Originally Posted by hpa1 View Post
    so does the spring hold it in this position as a default?
    Yes

    Quote Originally Posted by hpa1 View Post
    I have tried this spring setup and I am lucky if I can get the brass nut 1/2 turn backwards on the shaft due to the spring tension.
    That's should be plenty that's 1.25mm of movement (though maybe not if clamping wood or some such?) There is something in my first post about 290Deg movement as Max anyway, though I dont recall the details.

    Quote Originally Posted by hpa1 View Post
    So by winding the brass nut to close the jaws that is the fast speed and then nipping the shaft up via the handle to lock in the work piece constitute the low gear/ speed. Does this sound like how the vice works?
    Not exactly, you maybe missing the clever part. There is no need to touch the brass part(though if you were moving the jaw a long way it maybe quicker?) just turn the handle. When there is no load the jaw moves at 12.7mm per turn, as soon as there is pressure on the jaw it "changes speed" to 2.5mm per turn. You dont need to do anything other than turn the handle.

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