I have a 3/8in drive "clicker" type torque wrench from Harbor freight which I have been meaning to check for a long time. Its the Pittsburg Pro 5 to 80 ft-lb model, all metal and with 1/2ft-lb graduations. I tested it using a bench vise mounted vertical to clamp the ratchet square drive in place and hold the torque wrench horizontal to my eye. The weight was a 40lb kettlebell showing 39lbs on my digital bath scale, and it was placed at 12in and 6in to check the wrench for 19.5ft-lbs and 39ft-lbs (naturally).
At 6in I needed to set the wrench at 18ft-lbs to achieve a click.
At 12in the wrench required a setting of 42ft-lbs to achieve a click.
This results in a +7.7% to -7.7% actual torque output respectively. The measurements seemed pretty consistent as I removed and replaced the weight a couple times each getting the same result, the weight was also removed to adjust the wrench to avoid any loaded bias.
I don't know/remember what the original spec's were for the accuracy, but I would venture probably in the +/-6% range so I figure this is pretty good. Any thoughts?
At 6in I needed to set the wrench at 18ft-lbs to achieve a click.
At 12in the wrench required a setting of 42ft-lbs to achieve a click.
This results in a +7.7% to -7.7% actual torque output respectively. The measurements seemed pretty consistent as I removed and replaced the weight a couple times each getting the same result, the weight was also removed to adjust the wrench to avoid any loaded bias.
I don't know/remember what the original spec's were for the accuracy, but I would venture probably in the +/-6% range so I figure this is pretty good. Any thoughts?