I use a Digital Torque Adapter. Not a cheap way of finding out how accurate your torque wrench is but it is an effective way.
My digital torque adapter is a Powerbuilt ½ drive unit from ALLTRADE tools based in Long Beach, CA. The calibration inspection paper of my unit states the most error it has is .3% (point three percent).
Powerbuilt Digital Torque Adapter - YouTube
I only use it to check out my torque wrenches. When I tested my buddy's cheap Harbor Freight Clicker torque wrench. At the setting of 50 ft-lbs, the torque adapter noted 53.4 for an error of 6.8% . At the setting of 80 ft-lbs the torque adapter noted 71.3 ft-lbs for an error of -10.88%. Needless to say, the torque wrench went to the garbage.
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