|gerry madden||12/01/2020 18:41:49|
|80 forum posts|
I'm just calculating the clamping force I can get using my large but ancient vice. Its mechanical advantage comes out at around 260 which would give some theoretically big forces but there must be some losses. Does anyone here have an experienced-based suggestions as to what this might be ? 10%, 50% 80% ?
|55 forum posts|
If it is a vice screw it can't be very efficient as that would not work for a vice. If it was more than about 50% efficient it would just backdrive instead of keeping something clamped.
So less than 50%, and probably not even close to that as vice manufactureres likely wanted to be able to work up pressure and keep things stuck.
|Andrew Johnston||12/01/2020 19:27:26|
5111 forum posts
The manufacturers data for my machine vice shows that the clamping force (lbs) is very roughly 90 times the torque (ft-lbs).
|gerry madden||12/01/2020 19:56:26|
|80 forum posts|
Thanks all. Vidar you put me on the right lines and got me thinking. I found lots of data for screwjacks and it comes down to lead angle of the thread and CoF at the thread. So in my case its going to be about 20%. And when plug this figure in I end up in Andrews ball-park ! Clever stuff, maths
|not done it yet||12/01/2020 19:57:46|
|3933 forum posts|
Look up ‘fireball tool’ for videos on testing vises. I expect there are others, too. Then work backwards.....
|Nick Hulme||12/01/2020 23:05:33|
|723 forum posts|
Your choice of friction modifier can make a difference.
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