On 15/07/2011 05:13, wrote:
How much force does a common shop vise develop in its jaws? Google was
pretty unhelpful on this - the only reference I could find suggested
up to 7000 lb. Another paper suggested that a minimum required
clamping force for machining is much less - up to 1000 N.

I am interested because I am trying to guess how much force I can
develop in this press:

http://www.flickr.com/photos/2768312...57622484352534

Right now my answer would be "not enough" (see the following photos if
you are interested in the process).

Can anybody suggest how such force could be measured?

Michael Koblic,
Campbell River, BC
It's easy to work out.
Let P = the pitch of the screw, and H = the length of the handle (this
is measured at the point where you grip the handle and is generally a
little less than the actual length).
The mechanical advantage of the system is then 2*Pi*H/P

Assuming the pitch is, say, 0.1", and the handle is 12" long, then the
mechanical advantage is 2*Pi*12/0.1 = 75.4/0.1 = 754
If you apply a force of 10Lb to the end of the handle, then the screw
will exert a force of 7540 Lb, assuming no losses due to friction.
Unfortunately, the frictional losses will be rather high, probably more
than 50%, so the actual force would be more like 3000 Lb.
IHTH

--
Regards, Gary Wooding
(To reply by email, change gug to goog in my address)