Break-Open Torque Wrenches Unreliable?

I use Dyna torque wrench and I didn't face any troubles, however the ratchet wrench of NBC also measures the torque up to 45.

I use the DynaTorque-type (Zimmer) wrench and had one single episode when the wrench wouldn't 'break' and resulted in over tightening the abutment screw. The wrench seems to be working now as I compared it to the PTS wrench (with plastic insert that snaps at pre-determined torque) , also from Zimmer. The Straumann type, seems to be very reliable.

Interesting question about the torque wrench. Ue use Lifecore Prima, and our rep told us that the wrench whould be autoclaved in the "broken" position to prolong its life and to keep the torque it disengages accurate.

I have all my torque wrench calibrated at least once a year.

Most of the torque wrench on the market function on the principle of a metal spring deformation of some kind. (more or less as a roman scale to describe in short!) When you expand and relax the spring so many times, you loose calibration, no matter what. The most accurate torque wrench to my knowledge is the Torque-Lock by Intra-Lock. It works on the principal of metal beam deformation, and reading is direct from 10 to 50Ncm. The gauge movement is relayed by rubis and sapphire gears. (as in a precise swiss watch). It doesn not loose calibration as fast as the others. But to be on the safe side, even this one must be caibrated every year or so.

Torque limiting wrenches have always had problems with reliability due to autoclaving. Regular calibration should be done to make sure that your instrument is functioning properly.

Interesting. How does one go about getting their torque wrenches calibrated?

Anthogyr manufactures the Torque Control, which is a highly reliable system that is unique in its design. It is not a ratchet design which leaves very simple to use, takes less space in the mouth, and is more accurate. Features 7 torque values from 10 to 35 N.cm.

I have 2 DynaTorq 30Ncm wrenches that locked up. I used WD40 on them and they appear to be working just fine now.

There is a reliability factor with any of the torque wrenches. The truth is, they should be calibrated the moment they begin to function differently, whether it is the elasticity of a metal or a plastic. In other words, if it is important enough, and I think it is, they should be checked as often as we use them. These instruments just are not manufactured with that kind of reliability.