Torque vs. clamping force

[ggarnier]

Is there any place to find data on fastener torque vs. clamping force?

Specifically (I'm embarassed not to have an intuitive grasp of this) if I get P# force with a fastener of one size at T ft-# torque, will I need more (or less) torque with a larger fastener to get the same P clamping force?

Thanks

 

[MarkRPflow]

Look at the AISC handbook, any structural steel design book, fastener catalog or vendor website.

Try this website:

http://www.fastenersources.com/

or

http://www.fastening.com

your right - this is elementry.

 

[PK]

Typically thr relation between the applied torque and the bolt and nut will vary tremendously due to the unknown true friction between the female and male thread. Typicaaly from the electric power research institute (EPRI) the simple relationship between bolt and nut is T(ft- lbs) = K*(D/12)*F; where K= nut factor for the bolt/nut= 0.2 (dry threads); D= nominal bolt size(inches); F= applied tensile force in the bolt (lbf).If the threads are lubricated then the nut factor can vary significantly depending upon lubricant. Typically the AISC will take bolted joints to 90% of yield which makes these fasterners one time use , since permanent elongation occurs to the bolt.An excellent bokk on bolted joints is " Bickford, An introduction to bolted joints", Marcel Dekker, Inc...........PK......

 

[ggarnier]

Thanks, PK -

If I may reiterate:

For constant F, the torque required to produce that force increases with fastener size.

Another way of stating this: increasing fastener size will make it more (not less) difficult to generate by hand the torque required to produce a specific axial force.

 

[hrvat]

The clamping force of the bolt also has a lot to do with the type of thread you are using (pitch or lead of the thread) and included angle of the thread profile. This calculation (in one form or another)is in probably all machine design textbooks ever written. Friction coefficients are also included in this calculation.