Torque - Force relationship in C-clamp. 1

[kingnero]

I know bolt calculation is only as correct as the guesses towards the K-factor,

however just for an indication:

What would be the pressure generated by a certain torque on the handle of a C-clamp?

Is this formula valid?
T = K F d
with d = nominal diameter of the threaded section

or is this one correct?
T = K F p
with p the pitch distance
as mentioned here ( a random google search)

I hope you will understand the question without the need for a drawing or a sketch, just imagine you're trying to squeeze a bathroom scale with a regular C-clamp...

 

[MikeHalloran]

Try this:

http://www.engineersedge.com/gears/screw-axial-thrust-load-calculation.htm

Mike Halloran
Pembroke Pines, FL, USA

 

[Cockroach]

You look at the C-Clamp as a curved beam, which would have a deflection once the screw is torqued to a predescribed level.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[racookpe1978]

Well, the wouldn't you need to first determine the "total available linear force" (from the spreadsheet for example) based on the torque applied (force applied times effective handle radius)?

Then this "total available force" is going to be divided into the clamping force, the bending force (of the C-clamp beam), friction losses in the screw thread as friction resistance increases.

So when does the C-clamp handle begin bending? 8<)

 

[kingnero]

I didn't really intend to go so deep into this, I just wanted to have an indication of the force.

I can live with a 25% error (it's for woodworking and glue - home hobby project), and I am not going to use excessive torque so I assume the bending or any other deformation to be very small or negligible.

In the meanwhile, I've confirmed the first formula to be correct, I just wasn't sure any more hence my original question.

 

[chicopee]

The equation that I would use for accuracy is the one presented in the link by MikeHalloran. This equation has all the variables and is the one discussed thoroughly in any Machine Design college course. The others that you presented are just short cuts.

 

[Tmoose]

While I was cyphering I'd orobably be tempted to throw in (or subtract?) a little something extra for friction in the small diameter ball and socket joint at the clamp's swiveling foot.

Dan T