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Thread: Two speed vice screw
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10th Oct 2011, 09:47 PM #1Most Valued Member
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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.
StuartLast edited by Stustoys; 10th Oct 2011 at 09:48 PM. Reason: spelling
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10th Oct 2011, 10:25 PM #2Dave J Guest
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
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10th Oct 2011, 10:38 PM #3
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
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10th Oct 2011, 10:45 PM #4Most Valued Member
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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.
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
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11th Oct 2011, 08:22 AM #5Distracted Member
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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.
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11th Oct 2011, 11:28 AM #6Most Valued Member
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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.
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11th Oct 2011, 12:32 PM #7Distracted Member
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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.
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11th Oct 2011, 02:17 PM #8Dave J Guest
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
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1st Jul 2019, 11:04 AM #9Senior Member
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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.
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2nd Jul 2019, 03:54 PM #10Most Valued Member
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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 4mmLast edited by Stustoys; 2nd Jul 2019 at 11:30 PM. Reason: typo
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4th Jul 2019, 12:55 PM #11Senior Member
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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?
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4th Jul 2019, 02:46 PM #12Most Valued Member
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Yes
Yes
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.
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.