Some insight gained from the selection and calibration process that we use for torque wrenches. When selecting a torque wrench never factor the lower 20% of the wrench for use. The wrenches we calibrate are calibrated from 20% to 100% of the range. Thus saying if you have a calibrated wrench it will be repeatable in the upper 80% to plus or minus the rated tolerance of the wrench. How long a torque wrench will hold its tolerance is generally dependent on the quality of the wrench. One interesting thing I learned calibrating wrenches was how critical you hand placement on the handle is. If you choke up on the handle or hold it out at the very end you can make a perfectly good torque wrench fail calibration. The proper position for loading the wrench is in the center of the handle.
