Skeptic68W
Well-known member
- Joined
- Jun 18, 2015
- Messages
- 416
So it has been bugging me recently that I have never had any of my torque wrenches calibrated. I considered having them calibrated, but to be honest, I'm just a DIY'er and the cost would be in excess of just purchasing new ones. 
I really hate the idea of just purchasing a new, cheap torque wrench every couple years (especially since I use 1/4 and 1/2, and occasionally 3/8), so I decided I would test the ones I own, and then either calibrate them if the mechanism is accessible, or replace them with ones that I can calibrate over and over again, achieving a long service life.
Here is how I went about my testing. It's nowhere near as exact as a certified calibration shop, but it's good enough for me.
I purchased the follow torque adapter: https://www.amazon.com/gp/product/B07DV33XJ5/?tag=atomicindus08-20
The adapter came with it's calibration card showing it passed the standard of 0.5% accuracy, and showing it's output against the standard at several different torque levels across the range. It was inside of 1 ft-lb at every torque level except the max (250 ft-lbs), which it was off by about 1.5 ft-lbs. A very good standard to check against for a redneck like me.
Yes, I know Harbor Freight sells one for 28 dollars, but that one has a minimum ft-lb spec of 29.5, where the AC Delco one goes all the way down to 4 ft-lbs, meaning I could use it to check my inch-lb torque wrench as well. Plus, I trust AC delco much more than HF.
I then torqued a lug nug on my truck to the maximum amount my biggest torque wrench will do. This ensured the nut wouldn't move and I would have a study base to work with. I was going to try to mount something in the vise, but it was just not working out and the truck was easy.
The process I followed was similar to what's found in this video:
I "exercised" each torque wrench at it's maximum setting 3-5 times before backing it down and testing various points. From there, I set the torque on the wrench, hooked it up to the adapter, took all the slack out, and then tried my best to slowly lean on the wrench until it clicked. I set the adapter to "peak" mode, which measures the first peak torque you hit, so when the wrench clicks, the adapter marks down that number and holds it on screen, even if you keep pressing on the wrench.
Now, I didn't get all nerdgasm on this and make a spreadsheet, instead I went for the volume approach, doing many tests at many torque settings, looking more for consistency than accuracy. The reason for this is that I had to use adapters on the 1/4 and 3/8 torque wrenches to get them to interface with the tool, thus losing some torque and affecting the reading, and second...because I didn't want to.
I own the following Torque Wrenches:
1/2: Craftsman Micro-Clicker: https://www.sears.com/craftsman-mic...SellerId=Sears&prdNo=1&blockNo=1&blockType=G1
I got this torque wrench as a gift from my father, brand new, about 5 years ago. It has been my main torque wrench. I used it to torque the head bolts on my truck last year...which really saddens me after today's test.
3/8: KD Tool 2951 (Old, USA Made)
Also a gift from Dear old Dad at the same time, however this was an ebay purchase, so who knows how old it is or how much use it's seen. It's got some wear on it, so I'd imagine it got used semi-professionally for a short period...that or the previous owner just didn't store it very well and it got knicked up.
1/4: Tekton 24320: https://www.amazon.com/dp/B00C5ZL2EG/?tag=atomicindus08-20
Purchased in February 2017 and used probably 3-4 times since.
All wrenches are always stored in their case, at the lowest setting, since I took ownership of them. Now, onto the results.
Craftyman: Boy, this was a disappointment. I expected it might be off a little, and need calibration (which I think is possible if you pop the cap off the bottom of the handle and use the nut and allen screw)...but it's not even worth trying to calibrate. The readings were all over the place. Measuring at 150 ft-lbs would regularly produce output anywhere from 125 - 175. Completely unaccepatable. It seemed to be worse at higher torque numbers. At 20 ft-lbs, it was pretty on, at 30, it was slightly worse, at 50, back to being pretty consistent, then at 70 and up, it was just garbage.
KD Tools: This was the wild card of the night. A used, old torque wrench with an unknown history. So far as I can tell, it's not user-adjustable with regard to calibration, so I had already resigned myself to throwing this one away, since I figure it was unlikely it would be accurate given it's age and condition. I've honestly never really used this torque wrench, just because I figured "I've got this Craftsman that was brand new, and I know I've always stored it properly and not used it at a breaker bar, so it's probably more reliable".
Turns out, I was dead wrong. The KD was BANG ON at pretty much every torque setting across it's range of 20 ft-lbs to 100 ft-lbs.
I was very surprised. The variance was often only a couple ft-lbs, not sure how accurate it is percentage wise, but I trust this thing for my uses. I wish I would have used it on my head bolts...
Tekton: Sadly, the Tekton didn't fair so well. I didn't write down any results, but it just seemed to me like there was a lot of variance in the readings at any given setting. I tried not to place much weight on accuracy with this one, since it had to be run through 2 adapters to get up to 1/2" drive, but rather, I was looking for repeat-ability of a given reading. Unfortunately, I didn't see that. Big swings of 20-30 in-lbs at a given setting was the norm.
So it looks like I will soon be in the market for a 1/2 drive torque wrench, and possibly a 1/4 drive as well. I might try buying a 1/4 to 1/2 adapter and retest to see if the tekton fairs better, but it seems unlikely since it was a variance problem and not an accuracy problem.
So yeah...old USA tools rule, as if we all needed any more reminders of that.
'MURICA
I really hate the idea of just purchasing a new, cheap torque wrench every couple years (especially since I use 1/4 and 1/2, and occasionally 3/8), so I decided I would test the ones I own, and then either calibrate them if the mechanism is accessible, or replace them with ones that I can calibrate over and over again, achieving a long service life.
Here is how I went about my testing. It's nowhere near as exact as a certified calibration shop, but it's good enough for me.
I purchased the follow torque adapter: https://www.amazon.com/gp/product/B07DV33XJ5/?tag=atomicindus08-20
The adapter came with it's calibration card showing it passed the standard of 0.5% accuracy, and showing it's output against the standard at several different torque levels across the range. It was inside of 1 ft-lb at every torque level except the max (250 ft-lbs), which it was off by about 1.5 ft-lbs. A very good standard to check against for a redneck like me.
Yes, I know Harbor Freight sells one for 28 dollars, but that one has a minimum ft-lb spec of 29.5, where the AC Delco one goes all the way down to 4 ft-lbs, meaning I could use it to check my inch-lb torque wrench as well. Plus, I trust AC delco much more than HF.
I then torqued a lug nug on my truck to the maximum amount my biggest torque wrench will do. This ensured the nut wouldn't move and I would have a study base to work with. I was going to try to mount something in the vise, but it was just not working out and the truck was easy.
The process I followed was similar to what's found in this video:
I "exercised" each torque wrench at it's maximum setting 3-5 times before backing it down and testing various points. From there, I set the torque on the wrench, hooked it up to the adapter, took all the slack out, and then tried my best to slowly lean on the wrench until it clicked. I set the adapter to "peak" mode, which measures the first peak torque you hit, so when the wrench clicks, the adapter marks down that number and holds it on screen, even if you keep pressing on the wrench.
Now, I didn't get all nerdgasm on this and make a spreadsheet, instead I went for the volume approach, doing many tests at many torque settings, looking more for consistency than accuracy. The reason for this is that I had to use adapters on the 1/4 and 3/8 torque wrenches to get them to interface with the tool, thus losing some torque and affecting the reading, and second...because I didn't want to.
I own the following Torque Wrenches:
1/2: Craftsman Micro-Clicker: https://www.sears.com/craftsman-mic...SellerId=Sears&prdNo=1&blockNo=1&blockType=G1
I got this torque wrench as a gift from my father, brand new, about 5 years ago. It has been my main torque wrench. I used it to torque the head bolts on my truck last year...which really saddens me after today's test.
3/8: KD Tool 2951 (Old, USA Made)
Also a gift from Dear old Dad at the same time, however this was an ebay purchase, so who knows how old it is or how much use it's seen. It's got some wear on it, so I'd imagine it got used semi-professionally for a short period...that or the previous owner just didn't store it very well and it got knicked up.
1/4: Tekton 24320: https://www.amazon.com/dp/B00C5ZL2EG/?tag=atomicindus08-20
Purchased in February 2017 and used probably 3-4 times since.
All wrenches are always stored in their case, at the lowest setting, since I took ownership of them. Now, onto the results.
Craftyman: Boy, this was a disappointment. I expected it might be off a little, and need calibration (which I think is possible if you pop the cap off the bottom of the handle and use the nut and allen screw)...but it's not even worth trying to calibrate. The readings were all over the place. Measuring at 150 ft-lbs would regularly produce output anywhere from 125 - 175. Completely unaccepatable. It seemed to be worse at higher torque numbers. At 20 ft-lbs, it was pretty on, at 30, it was slightly worse, at 50, back to being pretty consistent, then at 70 and up, it was just garbage.
KD Tools: This was the wild card of the night. A used, old torque wrench with an unknown history. So far as I can tell, it's not user-adjustable with regard to calibration, so I had already resigned myself to throwing this one away, since I figure it was unlikely it would be accurate given it's age and condition. I've honestly never really used this torque wrench, just because I figured "I've got this Craftsman that was brand new, and I know I've always stored it properly and not used it at a breaker bar, so it's probably more reliable".
Turns out, I was dead wrong. The KD was BANG ON at pretty much every torque setting across it's range of 20 ft-lbs to 100 ft-lbs.
I was very surprised. The variance was often only a couple ft-lbs, not sure how accurate it is percentage wise, but I trust this thing for my uses. I wish I would have used it on my head bolts...Tekton: Sadly, the Tekton didn't fair so well. I didn't write down any results, but it just seemed to me like there was a lot of variance in the readings at any given setting. I tried not to place much weight on accuracy with this one, since it had to be run through 2 adapters to get up to 1/2" drive, but rather, I was looking for repeat-ability of a given reading. Unfortunately, I didn't see that. Big swings of 20-30 in-lbs at a given setting was the norm.
So it looks like I will soon be in the market for a 1/2 drive torque wrench, and possibly a 1/4 drive as well. I might try buying a 1/4 to 1/2 adapter and retest to see if the tekton fairs better, but it seems unlikely since it was a variance problem and not an accuracy problem.
So yeah...old USA tools rule, as if we all needed any more reminders of that.
'MURICA
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