I unscrewed my wrench too far and had to send it out for re-calibration. Cost $65 and took 2 weeks. Then I ran across this on Amazon; Alltrade 940759 Powerbuilt Digital Torque Adaptor for 1/2-Inch Driver. Sounds like a pretty good device. Either way, having an accurate device is super important when cranking the bolts almost to the point of snapping.