Measuring impact gun torque?

[m_c]

You haven't, what I suggested is a tubular clutch that you tighten onto a shaft in a vice, very simple and close to a dynamometer, no nut or thread involved ;-)

I think I just heard a penny drop!
I'll give that a try when I get time, as well as playing with the springy washers.

[magicniner]

as well as playing with the springy washers.

For this you should use the best available friction modifier on the thread to minimise the difference between short sharp impulses and manual torque wrench, Tungsten Disulphide paste is best (but dificult to get, I had to import my stock) as it's coefficient of friction decreases at higher pressures, where Molybdenum Disulphide's coefficient of friction drops,

- Nick

[m_c]

I had a quick play tonight.

Tightening the nut/bolt/washers seemed to max out around 75Nm. Setting the torque wrench to 70Nm there was no noticeable movement, 80Nm things definetly moved, and 75Nm there was slight movement.

Slackening on the other hand, tightening the nut to 120Nm (starting to push the limit of the M12 8.8 nut/bolt), the gun managed to slacken it after a couple seconds.

The values are around what I would of guessed the impact gun would be capable of, and correspond to the calculated figures for tightening at partial power.
These measurements were to work out the feasibility of replacing this electric impact gun with a stepper/servo motor and gearbox to get a more consistent torque, however the cheapest planetary gearbox capable of the required torque I've found so far works out at over £300 delivered :-/

So it's back to either a new electric impact gun, or an air impact gun, but I only have about 8 1/2" between the top of the socket, and an immovable object.