I recently (read: nearly two years ago ) got given a "clicky" torque wrench which had seen slightly better days. I've spent a little time on it today, got the ratchet working properly, and now it clicks when a small amount of force is applied with the scale at one end and when a lot of force is applied with the scale at the other end. The problem is that the screw that secures the scale to the slidey bit (are you following this?), and I think you would use to callibrate it, was loose, so I've got no real idea at all where it should be.

Has anyone any experience of callibrating one of these, and a got a fairly easy and simple method? I've had a quick look on Google and seen all sorts of suggestions but so far the most sensible (apart from the obvious of paying someone else) way seems to be to clamp the square in a vice, use a weight, a pulley and some string, and calculate the moment by measuring how far away from the centre of the ratchet you have the string.

Any other suggestions?

I'm sorry for the useless reply, but I'll post it anyway
When I bought my nice teng tool expensive torque wrench, I asked about it going out of calibration, response I got was
:"it's cheaper to buy a new one than to have it calibrated by a tool shop or other professional"

Just buy a new one

Luke,
this one seems fairly straightforward, as long as you've got some weights with known values.
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If you wanted to be fussy, you'd arrange for the wrench to be vertical, with a cable and pulley setup to apply a horizontal pull to the handle.

Maybe best to concentrate on that part of the scale which you'll be using most frequently, although checks towards the upper and lower end of its range would be useful as well.

Might dig out those 56lb and 28 lb weights tomorrow, if there's a spare 'moment', to check the calibration of my 2 wrenches...

ken.

Weights are a good way to calibrate them as above. However if you can find a friend with a known accurate torque wrench you can set yours up quite easily. Use a 19mm set screw (bolt with thread right up to the head), suitable washer and nut. Place the nut in your vice, oil the thread, put the washer on the set screw, oil it well, and screw it loosely into the nut. Use your friends torque wrench to nip it up to 30lb ft and use tippex to mark the nut/set screw position. Then use your torque wrench to try to tighten it. When not enough torque is applied the wrench will click before it moves the nut. Keep increasing the setting until the nut just moves (tippex line broken) as it clicks. Then back off your wrench a tad and tighten the scale screw(s) so it reads 30lb ft.

Repeat this procedure but use yours to torque the set screw and get your friends to check it. You may have to adjust the scale again slightly. Once you are happy with this 30lb ft setting move up to 60lb ft and then down to 10lb ft. You may find yours is slightly more accurate at lighter torques than heavier.

Provided your wrench spring hasn't been damaged in the past this should calibrate it to within a couple of percent accuracy.

There's a bloke in our company that does calibrations.
If you're not in any particular hurry then feel free to post it to me and I'll get it sorted out for you.