Aproximating nut torque

[enginesrus]

thread404-107427

I'm being a bit lazy, its just easier to ask, and maybe someone has some fancy computer simulation software to nail it. I am jumping the gun though since I do not have the thread pitch and diameter just yet.
I have two items that I have to torque nuts on with no easy way to hold them to use any sort of lever wrench on, I can only use an impact wrench. So I can load the nut down maybe only a few inch lbs not sure how many yet, and then torque turn to get into the 185 to 200 ft lbs region. Any quick formula to accomplish that?

 

[enginesrus]

Using the stretch would be easy. This is not an easy stretch deal its on a shaft, it is not a bolt. I got them tight done good enough. They could not be held in a vise or any other way except building an expensive fixture.
Only tool that can torque something held by hand is an impact wrench.

 

[IRstuff]

As SwinnyGG described, if you have access to the nut, you can see how many threads it moves, which means you can determine how much it stretched.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[enginesrus]

I was not worried nor did I care what the stretch is or was. I just needed the equivalent turn angle that would produce X amount of torque. There is no specified stretch, for that matter no one even knows except for the manufacture what the real specified torque is. This is not a connecting rod bolt, it holds a ball bearing on the end of a shaft, the stretch on it would be extremely small the distance from nut face to the flange is maybe .625 or so, with no accurate way to even try to check stretch with out a surface plate and the gauges for it, that cancels out the option of measuring stretch.

 

[TugboatEng]

You've got it backwards. Stretch is what you are trying to achieve. Torque is just a really crude way of getting there.

If your application is so rudimentary why is all of this so critical?

 

[SwinnyGG]

Surface plate?

If you have a magnet base and a dial indicator you can measure stretch to the nearest tenth.. that's more than enough even in a short grip length application.

 

[rather_be_riding]

@SwinnyGG

You can also use ultrasonic bolt meter/gauge. Probably a bit easier and a rather convenient approach when you have a bunch of bolts to tension and monitor.

 

[SwinnyGG]

OP is a mechanic, I can almost guarantee he does not have an ultrasonic bolt gauge, but does have a dial indicator and mag base. But you're not wrong.

 

[enginesrus]

OP is an engineer / mechanic / machinist, knows about stretch, knows how to use an indicator, knows how to accurately use an indicator. This part would need a surface plate and 2" blocks to locate on to use an
indicator. There is no way to support the indicator with a mag base, then remove it to tighten the nut, and relocate the mag base. The impact vibrations would disturb it if left on the part, the indicator would be in the way of the socket.
I don't have a bunch of 30mm bolts that are 1 inch long to test with.

 

[rather_be_riding]

Well, sounds like you're going with the turn method then. Good luck with it.

 

[Kwan]

Would load indicating washers work?

https://www.pccfasteners.com/assets...iterature/pli_brochure.pdf?fireglass_rsn=true