What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Torque wrench for low values - 30 in-lbs

FlyGuy65

Well Known Member
What are folks using for torque wrenches for 25~30 in-lbs?

I have an old MiT/Tekton/Avery 20~200 in-lb wrench from 20 years ago. Did some testing and calibrating (calibrated at 95 in-lbs, verified at 47.5 in-lbs), and found out it reads 5~10 in-lbs off at the lower range (3lb weight at 9.5 in, should click at 28.5 but clicks until the 35 or so setting is dialed in). Some web surfing reveals that most wrenches are accurate from 20% to 100% of full scale, meaning a wrench with a maximum reading of 125 in-lbs would be needed to accurately measure 25 in-lbs.

It's certainly possible I did not store the wrench at the lowest setting, but would that account for poor low end accuracy after recalibrating in the mid range?

I suppose I could set the wrench to click at 30 in-lbs and press on, regardless of what value it's supposed to be set for, but I would like something that I can reliably set and use.

Thanks!
 
Last edited:
For very low torques, I use a torque screwdriver or (my secret weapon) a modern bicycle torque wrench which goes to very low values of torque. It’s really important with modern carbon-fiber bike frames not to over torque attachments, or you can crush and crack fibers, so there are accurate low torque wrenches available. Of course, they are in Newton-meters, so you’ll have to convert.... ;)
 
eBay Sturtevant Beam Torque Wrenches

I was really successful in purchasing older beam style Sturtevant torque wrenches from eBay. I got a 1/4" drive to do everything under 100 in-lb, and a 3/8" drive to do everything else. Because they rely on bending modulus of the steel, they're always accurate, and there is no forgetting to unset them.

Also, at a previous employer we had an issue where a particularly critical location fastener was clearly being under-torqued, despite using a Snap-On digital torque wrench. We mapped the torque from it and found at the lower 20% of it's range, where it claimed accuracy, it was off by as much as 40% (torque to 14 was actually 10 ft lb). That's bad.
 
This appears most popular if the form factor works- I like mine.
10-65 inch pounds in 5 unit increments

Wheeler Firearms Accurizing Torque Wrench with Inch/Pounds Measurement, Bits and Storage Case $50.

f3d5f95f-22d2-4970-a919-ba2a0ea55e72_1.5af649c9570b56fd8b9cf90078e4fcc0.jpeg
 
For very low torques, I use a torque screwdriver or (my secret weapon) a modern bicycle torque wrench which goes to very low values of torque. It’s really important with modern carbon-fiber bike frames not to over torque attachments, or you can crush and crack fibers, so there are accurate low torque wrenches available. Of course, they are in Newton-meters, so you’ll have to convert.... ;)

Same here. I use a Park Tools bike torque wrench for anything up to 15 N-m. I bought it years ago for my carbon fiber bike. It goes down to zero N-m if needed. I wrote up a conversation table with a list of settings for AN3, AN4, AN5, etc bolts that I taped to the wall above my workbench. A guy in the next hangar has the $500 big wrench that I borrow for anything above 15.
 
Well, it's been a long trip down the rabbit-hole, but at least it did put the 'learning' back in AEB.

I think I failed to dial the torque back down last time I used it (probably many years ago), and so that lower range is just not very reliable. Also wasn't adding in the torque needed for the AN365 nuts, so really looking at about 28~30 in-lbs.

FWIW I emailed Tekton, and they said their wrench was accurate to +-4% clockwise throughout the stated range (10-150 in lbs for the TRQ21101). Anyone used both the Tekton and the CDI and can compare?
 
What are folks using for torque wrenches for 25~30 in-lbs?

I have an old MiT/Tekton/Avery 20~200 in-lb wrench from 20 years ago. Did some testing and calibrating (calibrated at 95 in-lbs, verified at 47.5 in-lbs), and found out it reads 5~10 in-lbs off at the lower range (3lb weight at 9.5 in, should click at 28.5 but clicks until the 35 or so setting is dialed in). Some web surfing reveals that most wrenches are accurate from 20% to 100% of full scale, meaning a wrench with a maximum reading of 125 in-lbs would be needed to accurately measure 25 in-lbs.

It's certainly possible I did not store the wrench at the lowest setting, but would that account for poor low end accuracy after recalibrating in the mid range?

I suppose I could set the wrench to click at 30 in-lbs and press on, regardless of what value it's supposed to be set for, but I would like something that I can reliably set and use.

Thanks!

Are you calibrating by hanging weights? If so, when you calibrated your wrench, did you subtract out the wrench's weight at the calibration point to rule out gravity? In other words, grab it by the head and let the handle rest on your scale. My wrench is right at 250g (~1/2 lb) at the handle and it's 12" long. To calibrate at 24 ft-in, i would need 2 lb of weight, total. minus the 0.5lb it's actually ~1.5 lb. The difference between 2 lb and 2.5 lb is 24 ft-in and 30 lb-in, respectively.

The difference could very well be due to that if you didn't factor it in.
 
I did use hanging weights, and I did not factor in the handle weight (I didn't know any better!).

But, would that be the cause of the problem if I was consistent in not adding the handle weight in the calculations? I realize the actual torque value would be 1/2 ft-lb or so higher than set on the wrench. My problem is that after calibrating at the higher weight, the expected result with a lower weight is about 20% off (value set on wrench is higher than calculated actual torque.)
 
I did use hanging weights, and I did not factor in the handle weight (I didn't know any better!).

But, would that be the cause of the problem if I was consistent in not adding the handle weight in the calculations? I realize the actual torque value would be 1/2 ft-lb or so higher than set on the wrench. My problem is that after calibrating at the higher weight, the expected result with a lower weight is about 20% off (value set on wrench is higher than calculated actual torque.)

Ahh no I misread what you wrote. It does sound like yours is off at the lower end even if it’s calibrated a bit high. Adjusting the calibration may help some. It’s worth a shot.

I have heard good things about the tekton you linked. I’ve almost bought it a few times.
 
Inspired by the recent article on torque wrench calibration in this month's Sport Aviation magazine, I went and checked my ol' Harbor Freight torque wrench that I used for the entire RV project, and found it to be way out of calibration, meaning it is likely that most or all my bolts are under torqued. After a little work, I managed to get the tool within a reasonable error at the 25 and 50 in-lb settings, so now I must go through, check, and re-torque every bolt in the plane. Won't be fun.

Best to check those clicky wrenches periodically!
 
Back
Top