torque wrench recalibration

I need to get my torque wrench recalibrated but not sure where to take it.Is there a place in Columbus Oh. that does this?
Thanks

We have snap on do ours-I think they send them out

sears will send it out for you, and do it for nothing if it's crapsman.

Look in the yellow pages under "Calibration". Usually the same places that calibrate gauges will do that sort of thing.

I just take mine into work with me and do it there... Same thing with my multi-meters, scales... etc..

It's very simple to calibrate it yourself:

- Clamp the square drive of your torque wrench into a vice so that the body of the wrench isn't touching anything.

- Rotate the wrench handle until it is perfectly horizontal.

- Measure 1.5 feet out from the center of the square drive.

- Hang a 30-lb weight with bailing wire at that exact spot (1.5 feet out from center of square drive).

- With the wrench set to 45 ft-lbs (1.5 feet x 30 lbs), you should get the click.

- Move the weight in and out until you can find the transition spot where it clicks and doesn't click.

- If your wrench is off, adjust as necessary. You should have an adjustment screw at the base of the handle.

This should produce an adjustment that is plenty accurate for our jeeps.

Other guys clamp it *vertical* in the vice, and pull on it with a fishing scale or something ... once you get the basic idea, there are many ways to test and adjust it.

If you have a beam-type torque wrench, you can't really adjust it. You have to test it to see how bad it's off. For example, if you *know* from your testing that you've applied 50 ft-lbs of torque, but the wrench says 45 ft-lbs of torque, then you know the wrench is reading 10% lower than actual torque. Next time you want to give a bolt 100 ft-lbs of actual torque, turn the beam wrench until it says 90 ft-lbs and you'll know you are actually applying 100 ft-lbs of torque.

Clear as mud? Let me know if you have any further questions.

.

Even though I don't need to do it right now (or do I?), that's awesome info., Montanaman. Thanks.

No need for torque wench. Just tightened fastener till it breaks,then back off 1/4 turn.

I'd never test a tourque wrench like that... it's hardly accurate in any situation. Best bet is to go with the store/ company that you purchased it from, or find a calibration shop, any other 'redneck' methods may and will get you into trouble fast. You know how the handles usually always have a ring cut into about the center? That's where the optimal accuracy will come from.... IE, put the center of your hand over that ring.

I calibrate torque wrenches using load cells, and adjust them within a 4% error of the indicated reading. My personal one is only 2% off of actual. When you need to depend on a steering linkage or a wheel to not fall off from either a too loose, or too tight fastner, why do something that is inaccurate?

another option finger tight with lots and lots of locktight, oh and say a prayer, lol

artsifrtsi said:

find a calibration shop, any other 'redneck' methods may and will get you into trouble fast. You know how the handles usually always have a ring cut into about the center? That's where the optimal accuracy will come from.... IE, put the center of your hand over that ring.

Click to expand...

Artsi ... thanks for sharing your opinion, but rest assured I'm not a "redneck." (The predudice some people have about Montana can be mind-boggling.)

I just finished the Pre-Med sequence at UM, and on my way to becoming an optometrist. As such, I had to take a lot of calculus-based physics to get accepted to a decent optometry school.

I can assure you there is nothing magical or mystical about measuring torque. Torque is simply a rotational force placed upon a central object. It's generally defined as force x radius. In our case the force is pounds of exertion, and the radius is the distance (in inches or feet) the force is being applied from the center of the object being turned. We were able to measure it very accurately in physics lab with simple devices.

You brought up a good point about the handle mounting. Yes, most beam-type torque wrenches I've ever seen either had a round ball for a handle, or a haft mounted on a center pin. The reason for that was to get a more accurate reading. If you tilted the handle while pulling, you would be pushing with your thumb, and pulling with the heal of your hand. That would cause the bar to bend more than if you gave it a straight pull, giving you an inaccurate reading. (Picture a strong-man bending a re-bar). THAT is why they tell you to pull evenly about the pin.

And yes, most newer torque wrenches have the ring in the center of the handle. In my example above, I should have made it more clear that the 1.5-foot measurement was just for illustration ... it would have been better to measure from the center of the square drive to the center of the handle, and mount the weights from there. It's simpler to give 1.5 feet as a nice round number. I was explaining the general concept.

BUT ... It's entirely possible to get an accurate measurement from the center of the square drive (which corresponds to the center of the bolt) to the center of the handle. Any known force applied at that distance from the center can be used to calculate torque. Feet from center x number of pounds applied. That's torque, plain and simple.

Now ... of course there will be some room for error, even in lab situations. If you've ever worked in a lab, I'm sure you know that all lab reports have to discuss possible sources of error. In my example above the error should be minimal. A decent tape measure is quite accurate. And even if the distance measurement is off by 1/16" (which is a pretty big mistake for anybody who knows how to use a measuring stick), the inaccuracy would be roughly 1/3 of 1% if we were measuring 1.5 feet.

The weights could also be a source of error. But ... I have a baby scale at home which can measure 30 lbs, +/- .5 ounce. So I can know with good precision, what force is being applied at what distance.

A far GREATER source of error with torque wrenches is the actual bolt you are tightening. How clean are the threads? How much lube is in there? How old and worn is the bolt and nut? How tight were the manufacturing tolerances of the bolt and nut? Those factors have a much, MUCH greater effect on the final "tightness" of the bolt than minor errors in the torque wrench itself. When manufacturers provide torque specs for bolts, they do that knowing full well there are gross inaccuracies in the process of tightening bolts -- including bolts for "steering linkages" and "wheels."

Now ... if we were working on the Space Shuttle, where all hardware is probably manufactured to extreme specs, and assembly conditions are very tightly controlled, perhaps it would be more necessary to shave every .1% -- I dunno. But for cars, any torque wrench can be accurately tested within the 4% you mentioned above.

And by the way ... the method I described above wasn't given to me by some "redneck" around a cave fire, it's been used and accepted for decades by many certified, professional mechanics who produce quality results.

It's easy to dismiss something as ignorant, without thinking it through. And it's easy to feel afraid when thinking of steering linkages breaking, or wheels falling off. But ... the logic you used above could be used against doing anything ourselves. If we wanted to rebuild their own engine, you could say "have you ever seen a piston knock a chunk out of an engine head?" If you want to walk down a long flight of stairs, wouldn't it be terrible to go tumbling head over heels? Whenever you want to do something, there will always be some "expert" there to tell you that you can't do that, and describe all kinds of scary scenarios.

I prefer to trust my own head. The method above is a time-tested, accurate way to measure the torque applied to a torque wrench. It's been used by many professional, certified mechanics over the years, and will work well for the home mechanic too.

Anyway,this post is getting WAAY too long. That's because you forced me to re-evaluate what I wrote -- which is a good thing. Debate can be good and productive, and I would look forward to hearing other opinions.

.

I forgot to mention ... the method I described above was from an automotive magazine about 15 years ago ... I THINK it was a VW mag, but can't remember. They interviewed a director of a calibration lab. He recommended that method as good for do-it-yourselfers.

For vehicle maintenance, ±4% deviation is more than acceptable. Working on high tech avionic weapon systems ±4% was about the norm, with an occasional ±2% on something extra critical. I think you'd be hard-pressed to find a typical torque wrench that's truly cal'd to within ±4%.

At one time I was in charge of ordering, controling and ensuring our tools were cal'd, and often I had to return torque wrenches to the manufacturer because they failed calibration. Typical deviations were 6-8% on wrenches advertised as 4%. There are wrenches that are cal'd to within ±2%, but they aren't nearly as common and are usually VERY expensive.

I'm guessing my Harbor Freight wrench is, at best, around 10%. I'd rather use this than nothing. There's no cal sticker on my elbow.

Yep, clean threads, and the proper assembly lube, and or loctite is the key to maintaining proper torque.
check out this link, these are the super professional versions.
http://www.skidmore-wilhelm.com/

I did some aerospace assembly, i can say that our torque wrenches were calibrated every 3 months or after so many uses given the load percentage on the wrench, or anytime they were droped more then 6", or in question for any reason.
The tolerances were kept within 2% forward or reverse.
I know normally the tolelance is 4% forward, and 6% reverse.

87manche said:

sears will send it out for you, and do it for nothing if it's crapsman.

Click to expand...

Sear does not guarantee the accuracy of their torque wrenchs. They refused to exchange mine when it was way off (clicking at 140 ftlbs when set for 90). The most they would do is give me a rebuild kit if the ratchet part broke. I checked the accuracy using a method similar to what montanaman described except using a fish scale instead of a weight. Oddly enough, Home Deport did a straight swap for their much nicer 0-250ftlb torque wrench. Incidentally, the Husky brand wrench was within 2% using my "redneck" calibration method.

Another fine example of redneck engineering... I had a bolt that needed torqued to 450-ftlbs but no torque wrench that'd go that high. I used a socket, breaker bar, 4' pipe, and a bathroom scale. Using the pipe as a cheater bar, I stood on the scale, gripping the pipe at 4.5' and lifted until the scale read 100lbs heavier.

lawsoncl said:

Another fine example of redneck engineering... I had a bolt that needed torqued to 450-ftlbs but no torque wrench that'd go that high. I used a socket, breaker bar, 4' pipe, and a bathroom scale. Using the pipe as a cheater bar, I stood on the scale, gripping the pipe at 4.5' and lifted until the scale read 100lbs heavier.

Click to expand...

That would do it. I saw something like that recommended in a book once ... weigh yourself and figure out how far out to stand on the bar ... your way is better tho. If your measurements and bath scale are correct, you have a very accurate torque on that nut.

Some people call it redneck- I think it's a great practical application of physics. Good job Montanaman.

Oh, yeah, Montanaman... if you'd read my first post you would have read into the fact that I work in a cal shop... an NIST traceable lab to be exact. I calibrate everything from physical/ dimentional to microwave equipment.

Yeah, meybe your method would be good for a wrench to use in an emergency, but for a rebuild or anything that is done other that to get back home, properly cal'd equipment is all that should be used.

JJacobs said:

Some people call it redneck- I think it's a great practical application of physics. Good job Montanaman.

Click to expand...

Thanks!!