Torque Wrench: is mine knackered?

[ophic]

Just adjusted my chain - fine. But tightening the axle nut, I found that 100Nm or 74ft-lb that my torque wrench was set to - just didn't feel very tight. Is this normal? It seems way below the "grunt and a half" measure that some people seem to use.

Not trusting the wrench, I've tightened it somewhat further. Am I likely to have damaged anything? Does anyone have any methods of testing the wrench?

[flymo]

Depends how long the handle is I guess, but 100Nm is pretty tough even on the 18" torque wrench I have.

If you have access to multiple torque wrenches whose ranges overlap, compare them at a number of points throughout the range and see if they "agree". I'm sure someone on the board in your neck of the woods will let you use theirs for comparative purposes.

Becareful not to overtighten them and wreck the rear spindel and nut. I have just got back from the dealer 40 mins ago after having them replace mine!! They say that it was a manufacturing default that caused the damage to the spindle however I think it may have been them when they assembled it!

See here for details.

[embee]

100Nm isn't all that much, 100N at 1m, 10kgf at 1m, 20kgf at 0,5m etc

If you weigh, say, 80kg and your wrench is 0.5m long it's only 1/4 of your weight.

You can do self-calibration if you really want.

Easiest simple check is like Ceri says, usually there's some way to link 2 wrenches together using loose square drives etc, set one to a value, set the other to a slightly lower value and pull one against the other, adjust the second one up until they both click more or less together.

Next method is with buckets of water (1 litre = 1 kg = 10Nm roughly (9.8 ) and measure the length of the bar. usually only suitable fror smaller values.

You can do tricks with bathroom scales, stand on it and lean on the wrench on a car wheel nut or similar, see how much weight you put on the wrench and measure the length, multiply.

The water one is in theory the most accurate, but all are approximate really. Handy if you work somewhere that has some calibration equipment

[ophic]

Originally Posted by flymo

Depends how long the handle is I guess, but 100Nm is pretty tough even on the 18" torque wrench I have.

Yeah mine is about 18" long.

Thanks for the responses everyone. I'll get the wrench checked somehow.