How to calibrate a (cheap) torque wrench

The math I used is: Nm = force x arm length , 126 = Force x 42 , so force = 126nm / 0,42m = 300N, = 30kg. ( 1kg=10N)

Putting aside almost everyone elses comments about calibrating the scales and what scales to use and what colour socks you should be wearing etc, it is a very useful video in that you are showing the basic principle of adjusting a torque wrench. I didn't realise that they were adjustable as I have never given it a thought. I will be checking mine now. thank you.

Always leave a wind up torque wrench in an unwound state!

If you’re going to make a video about torque wrenches, make sure you always leave a tip by saying always take the tension off the spring in there before you put it back on a shelf for any period of time. Any spring left under tension will diminish in storage. Never adjust a torque wrench to like 240 ft/lbs, do a bearing and then stick it back in the tool box to store without taking all the tension off.

You can eliminate the imprecision of the spring scale by using the water vessel directly on the torque wrench. Hang the vessel on the wrench and add water using a measuring cylinder in precise quantities. I used a similar set up to set the dynamic torque value when preloading the input bearing on a differential. 2:11 btw. This adjustment is merely a zero. To fully calibrate a scale there needs to be a span adjustment too. to compensate for nonlinearity in the mechanism. This is why I recommend using the weight of water directly

Welll... you learn something new everyday, i was today old when i learned you have to calibrate a torque wrench. The more you know the better, knowledge is everything!

Allrighty folks, since this video got a lot of comments, I'd like to thank you all for watching. I'll make a Part 2 to adress some questions and do a follow-up. The math I used is: Nm = force x armlength , 126 = Force x 42 , so force = 126nm / 0,42m = 300N, = 30kg. ( 1kg=10N) Please note that this video is intended for home mechanics who want to check if their torque wrench is in spec. If you do customer work, you might want to get an expensive torque wrench and have it regularly calibrated. If any torque wrench manufacturer is watching this and feels the need to send a home mechanic on a budget a nifty torque wrench, please contact me!

That is exactly the type of torque wrench I have, so for me this instruction was perfect!

Until seeing this video I was content with knowing bolts at least were tightened equally. Now I must see if it is in fact accurate. Thank you sir. Great video

Unfortunately as an aircraft mechanic I cannot self calibrate as I have too provide a certificate. This is superb for diy mechanics . Kudos to you

wow. This is the first time I've ever heard about this kind of a wrench.

Schwarzenegger? No one better to discuss torque. Thanks for this video. Always figured my inaccurate torque wrench was better than my guesstimation. Now I'll sleep better.

Nice video Arnold. I would say this … a lot of people like to comment on other peoples videos about things they should have done or not. People kind of miss the purpose of the video , which is showing other a DIY process. Personally wanted to say thank you for taking the time to share this DIY process. Good job.

It’s my understanding that the force needs to be applied to the center of the knurled handle. That may be the purpose of the groove in it.

I could be wrong, but I failry sure the smooth groove in the knurling of the handle is actually the calibration point for your spring scale, rather than the tip end of the handle.

This was mega helpful and answered a question that was lingering in my mind. Thank you!

Extremely helpful Arnold, had an old one like this for years and years but one time my young son got his hands on it and suddenly it was in pieces, I reassembled it but was never happy so just purchased a new digital one, had I seen your video sooner I could’ve saved a $150, so now armed with this new info it’s time to play with my old torque wrench😃, thanks for sharing Arnold.👍

Then applying force to the torque arm, always make sure the load you are applying is perpendicular (and stays perpendicular as it winds up) to the torque arm, or you won't be torqing with the load you're measuring. Also, make sure it's on plane for the same reason.

notice the torque wrench was adjusted fairly high when you 1st showed it. Instructions with all my torque wenches say to back off setting to lowest (10ft #) for storage.

Interesting! I have a similar torque wrench, purchased in 1984 new for $25. I guess I should probably calibrate it. 🤪