WORKSHOP circumstances, a wrench should be recalibrated every 10,000 cycles or 12 months. However, if a wrench is dropped, this can alter the positioning of the spring and roller bearing inside, affecting calibration accuracy. It is also possible to over-torque( when the wrench travels past the torque setting without a definite release and continues to apply torque beyond the set value). This can happen on lower quality wrenches as the release‘ click’ may not be very audible or have less of a tacticale feel, especially at lower settings.
What are the most common maintenance issues? Often the ratchet mechanism needs cleaning as it’ s metal against metal clicking which affects the teeth. Spring length adjustment and replacing worn parts such as shims and blocks are other routine maintenance procedures.
Do you need to wind a wrench off after each use? If using a micrometer spring type, yes. If they are left wound up, then the spring can weaken or‘ take a set’ over time which again affects calibration, so a spring wrench should be returned to its lowest setting after use to help prevent this. A torque wrench is a sensitive measuring instrument and it should be treated like one – never use it as a breaker bar either.
What’ s the difference between cheap and expensive? Construction and calibration are the main areas. On a basic wrench, a mild steel spring may be used as it’ s cheaper, but using lower
tensile materials like this will start giving different readings after as little as 200 readings or so. Mass-produced wrenches are made to a set tolerance and are only tested at random, not individually, to validate this tolerance. When wrenches are calibrated, in order to apply torque at a set rate, speed and uniform pressure, specialised calibration equipment must be used.
Does an extension affect the torque setting? When using a vertical extension between the socket and the torque wrench, there is no change to the torque being applied, but using a horizontal extension will affect the torque being applied. A calculation will need to factor that in, or you risk over-tightening your fastener.
94 KIWI RIDER