Transfer from Axial Load to Torque in Thread

No.

Lts close the topic before it gets out of hand!

Tornado is correct. Remember, torque is τ = r × F, and since the force is applied along the axis, the magnitude of r is zero, thus, the torque is zero.

Not clear what you're asking. If by "....there is no any relative movement between nut and bolt (self-locked)" you mean the nut and bolt are fixed together, eg welded or Loctited, the nut/bolt might as well be one solid piece, and the answer is obviously no.

Now it is ut of hand! I knew it!

Can you agree to "no"?

Due to the flank angle P/(2*π*d2) a torque will occur. Because of the friction if it is big enough and the pitch is small the nut will NOT move because sliding is not possible.

The torque is Faxial*sin (above angle)* d2/2 where d2 is the mean diameter of thread.

A force on a nut is an external force and the contact nut bolt is made on the flanks.

Surprised by above answers.

That's right if the nut is free to rotate on the bolt. I was about to comment that it depends on the values of thread pitch hence angle of thread to the bolt axis, and the friction coefficient. But OP said the nut and bolt are fixed together, which pretty much answers his own question (in the negative) IMHO.

Maybe IdeaSmith has the right idea

Post No.6 and No.7 is correct - I agree with the views expressed byMr.Nickname and Mr.Codemaster

DHAYANANDHAN.S

Thank you very much!

He writes only that there is a "selflocking" situation which ONLY means that the force along the flank is smaller than the friction force due to the normal component. this means ONLY that the nut will not TURN but this deos not mean that the force does not generate a torque.

Make a sketch an all is clear thus my surprise with respect to the answers.

That may be what he means by "selflocking" but I don't think it's clear. That's why I posted #4 asking him to clarify. I doubt whether he's put much thought into the BALANCE between tendency to TURN and friction, or he'd be able to work it out for himself.

Nick's No.6 and Codemaster's No.7 (the first part) are correct (GA from me). A perfect real world example is backdriving a high efficiency ball screw. If you apply axial load to the screw it will cause the nut to rotate with a significant amount of torque. It's the reason why we always use brake motors for ball screw applications. Same applies for a standard nut and bolt. As Nick mentioned, friction is the reason why a standard nut will not move but the torque is still present. I too am surprised but some of the earlier answers.

After thinking about again (a few hours later). I may have to take back what I said. The ball screw example is valid because the nut rotates thus imparting torque to whatever would be there to stop it from rotating (an external component). In the case of a standard nut and screw, the nut does not rotate due to friction between it and the screw. Since it does not rotate relative to an external component it does not impart any torque.

So I guess...I dunno!...too distracted at the moment.

I'm astounded by some of the "answers" here

Assuming that ShuiShous has made the common mistake of writing 'torque' when he actually means bolt stress, then yes, of course, tension is applied to the bolt. However, such axial load is only temporary unless the nut can be turned down to the the spotface whilst the load is being applied and held. Thus, after the load has been released, the nut "locks-in" the resultant stretch. Hence the joint becomes "tighter".

This is basic bolt tensioning. Obviously, and quite surprisingly, many aren't aware of it. For the benefit of those don't know, here's a link to a page explaining the process: Bolt Tensioning: How it Works

Can't see why you should assume he has made the common mistake (if such it be) of writing 'torque' when he actually means bolt stress.

There are quite a few of us on this forum who understand the issues of bolt tightening pretty well, it's come up a few times. But as far as I can tell the OP isn't asking about ordinary bolt tightening, with the need to produce correct bolt preload, but something different.

Your link shows only one way of tightening. There are plenty of others, torque wrench, experience etc. No doubt hydraulic tensioning is an excellent method, but there must be millions of bolts tightened every day throughout the world, and I'd guess only a small fraction are done with such sophisticated methods.

I am not changing my earlier answer.