Tools: What torque wrench to buy

[confused_al]

This site is great to get your conversion,
http://www.unitconversion.org/unit_conv ... orque.html

[alexpia]

i have a snap on tech2100 3/8 drive one its expensive but worth every penny. its electronic. had a1/2 inch one someone borrowed it and never got it back. i work on busses so an expensive one is justifiable. i have a craftsman 1/2 in. digitork one and it has worked ok on older volvos but on 850 or newer i believe u will need a torque angle wrench.

[jreed]

I realize I'm reviving an old thread, but since it mentions torque wrenches, Harbor Freight and calibrations I thought it would fit in OK.
I recently got a Quinn digital torque adapter which records peak torque and used it to test out my 3/8" and 1/2" drive HF torque wrenches that I've had and been using for about 10 years... just to see how accurate they were.
The 3/8" drive wrench was still pretty accurate and linear, giving 83 ft-lbs at a full scale setting of 80 ft-lbs (+4% error). At all settings, it was generally reading 1-3 ft-lbs higher than its setting. For me the critical one is spark plugs which I torque to 18 ft-lbs. On this wrench, the average peak torque was 19.3 ft-lbs (+7% error). Not too bad, and good enough for the job... but next time I use it I'll probably install the Quinn adapter in line and set the wrench to 17 ft-lbs to try to hit closer to 18 ft-lbs on the spark plugs.

3/8" drive Harbor Freight torque wrench calibration. All units in pound-feet [lb-ft]

3-8%22 drive torque wrench.png (68.47 KiB) Viewed 489 times

I'll post the results of the 1/2" drive wrench next... it was not as accurate.

[jreed]

Here's the data for the 1/2" wrench. It was off by 10% (on the low side) at full scale.

1-2%22 Drive Torque Wrench.png (86.27 KiB) Viewed 469 times

I also measured my 1/4" drive wrench. It was closer, but read 6% on the low side at full scale.

1-4%22 drive tqrque wrench.png (86.47 KiB) Viewed 469 times

So far, I'm happy with the digital torque adapter from Harbor Freight and I'd recommend it to anybody here who has old torque wrenches like me. I noticed that the fits to all the data were >99%, indicating that the digital gauge and torque wrenches are pretty linear, which is good. But the digital gauge is indicating that the 1/2" and 1/4" drive torque wrenches are outside their 4% calibration spec, both on the low side. The 3/8" wrench was at the 4% limit on the high side. I plan on using the digital torque adapter instead of relying only on the click from the torque wrench.

[abscate]

Something to remember before getting to torqued up about this



What you are really trying to set , most of the time , on a fastener, is tension,the holding force on what ever it is clamping. The torque or twist you measure on the fastener head is an indicator of this and goes up as the tension increases, all good.

The forces you are overcoming are tension in the bolt, friction inthe threads, and friction in the head...all roughly equal. Only the first one impacts fastener clamp force, though, and if the friction in these changes, your twist measurement no longer reflects the same fastener tension

Upshot.,,,torque as a surrogate for fastener tension is accurate to about 20% , generally accepted.

You can help your self do better y by cleaning threads,lube, chasing threads, filing off scarf/ rust on surfaces, etc.