Bolt Torque Question
Bolt Torque Question
(OP)
I have a bolt without any friction information.
T=FDK
D=0.008m
Tmax=20Nm
K= ??? unknow friction factor
It was tested and Tavg(old)=2Nm.
The same bolt was coated and the friction has increased.
It was tested and Tavg(new)=9.8Nm
I know the relation 4.65Tavg(old)=Tavg(new)
If both bolt was torqued to Tmax=20Nm on a torque wrench, would the clamping force be the same?
ANY HELP OR GUIDANCE WOULD BE APPRECIATED. THANKS
T=FDK
D=0.008m
Tmax=20Nm
K= ??? unknow friction factor
It was tested and Tavg(old)=2Nm.
The same bolt was coated and the friction has increased.
It was tested and Tavg(new)=9.8Nm
I know the relation 4.65Tavg(old)=Tavg(new)
If both bolt was torqued to Tmax=20Nm on a torque wrench, would the clamping force be the same?
ANY HELP OR GUIDANCE WOULD BE APPRECIATED. THANKS





RE: Bolt Torque Question
I'm not completely following what you are saying, how are they testing the bolt???
However if you torque tighten two bolts with the same thread and both are either lubricated or not, then in theory the clamping force would be the same but in practice the clamping force could vary between each bolt by as much as 40% because torque is not a very accurate way to control clamping force.
RE: Bolt Torque Question
So Tavg were measured for both bolt condition.
This is the same bolt, same thread, only thing changed was the coating on the bolt thread.
RE: Bolt Torque Question
The increase in wrenching torque you describe after coating the bolt threads is likely due to interference between the mating threads caused by excessive coating thickness. The prevailing torque does not contribute to axial preload. However, the prevailing torque does contribute to the self-locking capability of the fastener.
RE: Bolt Torque Question
RE: Bolt Torque Question
How do i find out what current friction factor is experimentally???
Then i can do the same experiment on the new coated bolt to find out friction factor experimentally.
RE: Bolt Torque Question
Try this link:-
http://www.google.co.uk/url?sa=t&rct=j&q=&...
A question for you, are you using some kind of prevailing torque nut or are these just ordinary threads.
RE: Bolt Torque Question
RE: Bolt Torque Question
http://www.iso.org/iso/catalogue_detail.htm?csnumb...
RE: Bolt Torque Question
RE: Bolt Torque Question
If the old tightening method presumably results in the fastener providing satisfactory clamping, measure the range of angles to which they are tightened.
Then, tighten a bunch of the new fasteners to the same angle while monitoring the maximum torquage.