Hi all,

is there any way to calibrate a torque wrench - I've borrowed one and I'm not convinced its right.... any suggestions?

Chris

easy
put the wrench output square part in a vice
get a big weight and a peice of string
see how far along the handle the string has to go to 'click' the wrench.
ftlbs of torque really are the ft along the handle multiplied by the lbs of weight!
cheers
Bob

Brilliant.... why didn't I think of that? Now to find a heavy enough weight...

Chris

depends on what sort of accuracy your after and what values you are looking to calibrate.

a couple of ways spring to mind.
attach a spring balance at a given distance from the pivot and pull.

or the method described, use 2l pop bottes filled with water or sand, the latter you need to weigh.

If you want bigger torques, fit a length of tuing over the handle - bear in mind the additional weight of the tube when doing the weight method.

Lastly if you have a good torque wrench, do up some bolts with that and then try yours, all that will you is if it is under or over - maybe good enough?

If you do this with a piece of tubing you will need also to take acount of the fact that the mass of the tube is at its mid point not at the point where you are hanging the weight

I send my wrenches back to sykes pickavant and in return they give you a nice certificate.

If its got a reverse would undoing a bolt of known tightness work?

i.e tighten a bolt in with a known wrench, then try and take it out with the unknown one set to the same torque, if it just clicks and won't drive then it must be reading under if its fine it must be ok or reading over.

Might give you a rough idea as to weather its right.

There's only one real accurate way,send it to your tool supplier or manufacturer.
You could of course borrow a friends(or two) and compare.
Dont forget to wind the tension off after use(sucking eggs),this does affect them after a while.

Just to put things in another perspective:

I send our depots 4 feet long wrenches off to be calibrated every six months.
These are constantly set at 450ft/lbs
for lorry wheels, and when peoples lives are at risk I dont take any chances.
(we have to leave them set to avoid mistakes)