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W0tzup t1_j45yiny wrote

Torque = force x radius.

If the force applied is constant but say the wrench is longer, then the torque generated will be more, and vice versa.

When you use a wrench with a preset amount of torque, it tightens the screw to that torque value and in order to loosen it up you will need to generate a minimum amount of that torque in the opposite direction.

The purpose of tightening screws/fittings to a specific torque value is so the thread does not get damaged; especially when you need to undo/redo them often.

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5J7XM33IXN4XCQI6B2BB t1_j46oexa wrote

The purpose of torquing is to apply a specific(ish) amount of preload to the screw. It has nothing to do with protecting the threads.

In many applications, a bolt can only be used once anyways because it stretches during torquing the first time it is used.

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Chasethemac t1_j471380 wrote

Protecting the threads is a huge factor in torque spec.

Material and thread type would determine what you can torque something, too. It's basically the starting point in determining a spec. Valve cover onto aluminum head, for example.

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5J7XM33IXN4XCQI6B2BB t1_j480mmf wrote

Torqued bolts/screws exist to provide a certain amount of clamping force. You do not choose a torque spec based on the threads, you choose the bolt size, material, and thread profile based on the clamping force requirements.

Anyways, I prefer angle control over torque control since it's much more repeatable, assuming your bolts are to spec.

I used to work for a fastener company in QA.

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minkey-on-the-loose t1_j46fvem wrote

Not only the thread, but the compression on a gasket, no?

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PsychoEngineer t1_j47bwob wrote

In a way; applying the torque translates into a force the screw/bolt head is applying axially down the screw/bolt into whatever it’s being driven into; this force is what holds the parts together, or in the sense of a gasket crushes the gasket a certain amount. (Think of the gasket like a spring not a solid).

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