robo

I always suspected there was something wrong with the cheap clicker torque wrench i purchased on eBay, one of those Harbor Freight types in the red plastic box.

My suspicions were confirmed when i rigged it up with another torque wrench, a big Craftsman beam type wrench. According to the beam wrench, the Harbor Freight wrench allowed torques almost 70% higher than the specified torque before clicking.

While the beam wrench is old, i'm assuming it is still fairly accurate, since it is so simple.

For example, when the Harbor Freight wrench was set to 120 in/lbs, it would not click until close to 200 in/lbs on the beam wrench's indicator.

I'm not sure if this thing can be calibrated, or if it's just a writeoff, but anyway, thought you guys might be interested and it might save someone some stripped bolts.

DMF 

I got 3/8" (not in red plastic box) that wouldn't release in one direction. So I returned it. The 1/4" I got (with red plastic box) works just fine.

Beam wrenches can go out of calibration. They depend on a material property that is not constant among all units, so there is a calibration setting. (Probably at the moving pivot in the case of the beam wrench.) Only testing against a known reference - e.g. freshly calibrated wrench, or moment arm setup - can show what's really going on.

HillRider

I believe beam wrenches can go out of calibration only if the pointer is bent so it doesn't indicate zero with no load. The properties of the beam itself won't change unless it is physically damaged. Clickers are routinely recalibrated against a beam wrench or a bench calibrator which is essentially a fixed mount beam wrench.

Hocam

You also have to be careful with the click wrenches to do the torquing from the very end of the wrench, otherwise it's not an exact reading.

Never used the beam wrenches, so can't comment on them.

San Rensho 

Beam wrenches will not go out of calibration, click wrenches will. If the pointer on the beam gets bent, just put it back to zero and you are set. I have both and I use the beam to check the accuracy of the click on a regular basis.

Clicks are nice for wrenching on cars, but for a bike, a beam is all you need and they are much cheaper.

robo

Hmm.. my wrench only releases in one direction, but i thought that was how it was designed (since usually you're only concerned about 'tightening' torque)... perhaps it's defective though.


As for the beam wrenches, i obviously don't know for sure, but it seems like common sense that they would be fairly stable in their adjustment (provided the pointer is pointing to the right spot, which is trivial to adjust). My beam wrench is basically a long thick bar of steel. I don't imagine the properties of that would change much under normal circumstances, barring corrosion or it being exposed to extreme temperatures. And since there is no adjustment possible, it would seem that if this type of wrench went out of adjustment often, one would have to keep throwing them out and buying new ones, which again, seems an unlikely scenario.

DMF 

Could be. They are supposed to work in both directions just like a regular ratchet drive. That way you can torque reverse threaded fasteners. (You should never use a torque wrench to break a bolt loose, even if it does have a conveniently long handle.)

The way I checked it was to clamp the drive (the little square bit) into a vise and do a reality check in both directions.

Btw, I wasn't objecting to using a beam wrench as a reality check, as you did. But you can't use it a calibration reference. Drifting or not, who nows how well it was calibrated to begin with?

twobikes

If there is doubt about the accuracy of a torque wrench, why not check it yourself? Torque is a force in pounds over a specified distance in feet or inches. Get a weight known to be ten pounds exactly and hang it from a horizontal bar ten inches long. Connect the torque wrench at the pivot point (zero inches) and pull until the ten pound weight begins to rise. The torque wrench should read 100 inch pounds. Even if a wrench is not designed for calibration, you should learn the factor by which to shift the readings given by the wrench for accurate results.