inaccurate torque wrenches

[dave friday]

Hi all,I was torqueing the head bolts with a click torque wrench [40,60nm] and it felt like 60nm was not very tight,so just as a check I tried using my bendy bar one 44.2ftlb/60nm..the click one was far too low [more like 50nm!].
Any comments?
Ta.

[AdrianC]

Any comments?

One of your torque wrenches is wrong... Better to be too low than too high.

[boatbuilder]

Same here just tested my clicker against my brothers bendy bar one and mine is way way lower. I think the spring wears out in the clickers.
I'm planning to get a bendy bar one for myself... less to go wrong with them.

[Titus A Duxass]

Cheap ones are notoriously inaccurate.
Leaving them loaded at a torque setting is death for the spring.

At work our torque wrenches cost about 200 - 400 € and require 2 yearly calibration so your B&Q 29,99 jobbie is basically - pants!

[dave friday]

I remember reading [in a vw publication] that the bendy bar type was to be used [on flywheel bolts?]
Something to do with pulling the click type a bit further after its clicked?

[Bubble Meister]

Torque wrenches should be calibrated regularly as they do creep. However the values you have given seem excessive. To put it into perspective the military standard simplified is this. I'll give examples in brackets for a 300Nm wrench
A wrench should work from 20 to 100% of its scale (60-300Nm). It should be accurate to 6% of full scale (3Nm) from 20 to 30% (so 20 % = 60 Nm plus or minus 18Nm) of full scale and 90 to 100%. In between 30 and 90% the accuracy should be 3% ( plus or minus 9Nm).

From this you can see that even if you wanted 40nm and that was the max the wrench could give then it should be plus or minus 2.4 Nm (6% of 40).
Have you got any friends in the aerospace, nuclear or similar as they must have torque wrench calibrators. We check ours every 3 months.

[dave friday]

Bubble, I have a mate who use to work in a weight standards lab [ in Kingston ] who says its very difficult [impossible] to have say exactly 1 oz as atmospheric pressure/humidity etc come into play!
But no I don't have friends in the fields you mentioned.