Patent ID: 8381568

Claim:
A method of obtaining same wrench torque by calibration by testing a plurality of different force exertion points on the hand grip of an electronic torque wrench, the electronic torque wrench including a wrench head for engaging a workpiece, a sensor having a forward end secured to the wrench head, an elongated wrench body having a forward end secured to a rear end of the sensor, a battery powered display mounted on the wrench body, a hand grip having a forward end secured to a rear end of the wrench body, two deformation members disposed on two opposite sides of the sensor respectively, and first and second adjustment holes in the sensor, the first and second adjustment holes being in communication each other, the method comprising steps of: (a) providing a calibration device comprising a test rod for simulating the wrench body, and a support plate on a rear end of the test rod, the support plate being for simulating the hand grip wherein on either side of top of the support plate there are provided at least two test points and an intermediate reference point, and the sensor is secured to a forward end of the test rod; (b) securing a forward end of the sensor to a stress gauge which measures a torque value obtained by converting deformations of the deformation members on the sensor; (c) placing two weights on the reference points and setting a count to one; (d) recording a torque value obtained by and shown on the stress gauge as a standard torque value; (e) placing a weight on a respective one of the test points on either side of the support plate; (f) recording a torque value obtained by and shown on the stress gauge as a test torque value; (g) comparing the test torque value with the standard torque value, obtaining a difference therebetween as an error, and determining whether the error is greater than one or not; (h) increasing bores of the first and second adjustment holes if the error is greater than one prior to looping back to step (e); (i) comparing the count with a predetermined count and ending the method if the count is equal to the predetermined count; and (j) placing the weight on another respective one of the test points on either side of the support plate and incrementing the count by one prior to looping back to step (f).