Load of a screw (SOS)

Simulation
1

Hi all

Another problem of calculation, a priori very stupid but I have a doubt.

I am trying to know the force given by a screw according to the tightening torque.
If I look at this site (www.pats.ch) for an M10 screw I find approx.90kN for a torque of 140Nm.
If I do a simple calculation: the torque gives a tangential force Ft=31kN (according to Ft=2C/D with C=140, D=0.009) which because of the helicoid gives an axial force "proportional" to the pitch: Fa=step/(Pi*D)*Ft=1.64kN

Thank you for telling me what I should believe.

2

Hello @Stefbeno

There is some data missing in the information you give us

Screw class - 6.8, 10.8 or 10.9
clamping accuracy between C10 and C59
The coefficient of friction (0.2 to 0.4) to obtain the minimum coefficient of friction at the parting line
The clamping method used (I guess here it will be with a torque wrench to better control the preload.

Are you sure of the torque of 140N.m is a lot for M10 screws it corresponds more to M16

Brief! :-)
for an M10 screw in quality 8.8 an average tightening accuracy of C20 (+ or - 20%) the tightening torque is 24N.m and F0min 14825 N min and F0max 30530 N. This value fluctuates quite a bit depending on the minimum coefficient of friction (parting line).

Kind regards

 

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3

To put it in context, it is a screw that is used to tighten a flange of a machining fixture that is being modified.

In fact, the goal is not to determine if the screw will hold (it currently holds) but what is the resulting force at the ends of the flange (where it presses on the workpiece).

The torque is applied via a puncture, the screw is in 10.8, the friction coefficient is "standard" (slightly greasy thanks to the cutting fluid that remains...)

Thank you @Zozo_mp 

4

In the end I based myself on this site: pats.ch, very interesting by the way that I will keep under my belt.

Comparing with the capabilities of other equipment of the same size, it should do it.

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