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Thread: Two speed vice screw
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10th October 2011, 09:47 PM #1GOLD 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 October 2011 at 09:48 PM. Reason: spelling
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10th October 2011 09:47 PM # ADSGoogle Adsense Advertisement
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10th October 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 October 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 October 2011, 10:45 PM #4GOLD 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 October 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 October 2011, 09:52 AM #6GOLD MEMBER
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Hi Bryan,
I thought the term "nut" might lead to some confussion.
There are really two nuts.
1. the nut that is bolted to the fixed jaw like most other vices with 2 tpi
2. the knurled brass nut seen in the picture with 2.5 tpi
Both are right hand threads.
The curclip pulls the moving jaw open and the spring ensures that the knurled brass nut moves to the start of its thread as the vice is undone.
I was going to try and explain more but I think I've come up with a way to show it with pictures. back soon.
Ok,
How it would look with the vice open and the work piece loose.
One full turn in, the shaft and the knurled nut have both moved together 1/2"(12.7mm). the jaws now touch the work piece stopping the knurled brass nut from turning with the shaft.
turning the handle roughly 45 degrees(see the line at the red arrow) . The line around the shaft has moved forward from 92.5mm to 88.5mm. The front of the knurled brass nut has only moved from 93mm to 91.5mm
The limit of the thread in the brass nut(line at arrow). The shaft has moved from 92.5mm to 79.5mm. the nut has moved from 93mm to 89mm.
There are some small errors in those numbers, not sure if its measuring/parallax errors or if there is something else going on.
StuartLast edited by Stustoys; 11th October 2011 at 11:25 AM. Reason: pictures
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11th October 2011, 11:28 AM #7GOLD 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 October 2011, 12:32 PM #8Distracted 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 October 2011, 02:17 PM #9Dave 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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