Torque wrench calibrations

[Dr. Diesel]

Some time ago, after experiencing problems with steel studs pulling out of aluminum castings, I decided to see what could be done about calibrating my torque wrenches. Long story short, I'm now equipped with certified digital torque analyzers, and can do the calibrating myself.

One of my torque wrenches, which has always only been absolutely babied, was out 18%!
Out of curiosity, I purchased three more, tested them, CALIBRATED them, then returned them. They were 8%, 11% and 9% out of whack, BRAND NEW!
I tried another test on one of them, before returning it. I put the head of the torque wrench on the bench, and let the handle fall to the bench from 6". The calibration was thrown out 2%! A careless "I'll just put this here" drop onto the bench, like I've seen many people do, threw the re-recalibrated wrench out 5%.
I've been told to handle these things like glass, and now I know why.
In aviation, it's the law to recalibrate everything (from wrenches to gauges) once per year. Judging by these tests and the carelessness of some people, I'd think every month would be more safe!

In any case, I'd like to offer a torque wrench calibrating service. I can calibrate from 10 in.lb to 250 ft.lb.

Prices:
Test wrench $30 Cdn.
Calibrate add $20 Cdn.
For each additional wrench in the order, subract 5% each.
Your choice of return shipping/insurance is not included in these prices.

This is half the cost of having a torque wrench tested and calibrated at any other certified calibration station.

It's well worth it, if you're concerned with continuing to perform high quality work.


Incidentally, being a dieselite like anyone else on here, barter (parts traded for labour) is considered fair trade!

 :wink:

[Rat407]

Calibrating torque wrench's is important.  Here in the Air Force we have all our wrenches done every 180 days.

Yes you have to be very careful handling the wrenches. It does not take much to get them out of spec.  Also for anyone that isn't informed you really need to store them in an enviromentally controlled room, like inside your house. Storing them in the garage where it the temp swings from one extreme to the next isn't good for them as well as humidity changes. Some may argue this but if you want your torque wrench to stay in specifications of what you want it to torque, proper care is imperative.

I have the lab on base check mine. I bought a craftsman 1/2 drive lbft wrench six years ago and it checks out fine with proper care. Granted it doesn't get used that much, just the usual tire rotation and head bolt torque.

Dr. Diesel, glad to see you offer a great service that is needed and is often questioned as to where someone can send their wrench to for calibration. The only issue I see is for those of us south of the border and dealing with all the mess of sending things up to the Great White North.

[jtanguay]

Were those clickers that you tested?  the beam style are supposedly the best... no moving parts

[Dr. Diesel]

yep, all clickers. I now believe that the only reason beam wrenches are considered better is that they're more difficult to throw out of calibration, and if that you can tell for sure if they are... the needle doesn't rest at zero.
Once a clicker wrench is in calibration, they seem to remain accurate until getting banged around or used a lot. Call it accuracy life. A calibrated clicker (probably beam wrench too) will hold it's calibration a certain number of repetitions before the accuracy starts to fall off. Different brand wrenches, storage/handling and average job torque all affect the accuracy life.

Dr. Diesel, glad to see you offer a great service that is needed and is often questioned as to where someone can send their wrench to for calibration. The only issue I see is for those of us south of the border and dealing with all the mess of sending things up to the Great White North.

Thanks for the vote!
I've found that shipping charges between the US and Canada (both ways) seems to often be cheaper than within canada (not sure about within the states) In any case, I can label them as warranty no charge and send an  invoice/calibration report seperately. That should result in no actual boarder crossing/duty/brokerage fees.

[firestorm13666]

Just wondering but where did you get the tools to calibration  torque wrenchs and how much did they cost,because i might get them myself.Thanks pm me if you like

[jackbombay]

I've wondered about the accuracy of my torque wrenches, I was going to make a tester myself.

  1 foot lever with a 50 pound weight on the end that has an old socket welded to it so I can hook the wrench up to it. Put a 3" extension on the wrench then hook it up to the "tester", then you need to place the extention on say the edge of a 2X4/top of a railing so your tester is rotating around a point that is 1' from your weight. Then pick up the weight with the 1' lever in the horizontal position. a 12" extension would be better to you could use your other hand to control it. Then adjust the wrench a pound at a time till it clicks, hopefully you're looking at 50 when it does click.
 [/shadetreemechanic]

[Dr. Diesel]

A decent torque analyzer goes for about $1300. Calibration is $250 per year, one direction only. US dollars.
You might get lucky and find a used one for $400-$500 US, plus calibration.

[745 turbogreasel]

Sometimes the Snap On Guy will test em for you.  My friend tested his Snap On against a Harbor Freight special, and much to our surprise, they were equaly close....

[DVST8R]

I am a Snap On dealer, and we have no equipment to test torque wrench's except against new torque wrench's. Cheap torque wrench's tend to be okay for about a year max, and then when you goto get them recalibrated they either can't be done or it costs you as much as a new one. :wink:

[Leumas]

Hi,

New to the Forum and found this post interesting.

I'm an aircraft mechanic working for a large company.  I am in charge of Tool Control for our hangar.  I test all our torque wrenches every 90 days and actually took a torque wrench calibration course just recently.

Not sure if any of the following is just common knowledge but I'll throw it out there anyway.

Click type torque wrenches

1.  Click-type torque wrenches with the twist grip need to be stored with the grip screwed all the way out.  This takes the stresses off the internal workings of the wrench.

2.  Before testing a torque wrench you should "exercise" the guts of the thing by screwing the grip fully in and out 2-3 times.   (I guess it wouldn't hurt to do this before any really important torque job either.)

3.  Always set the wrench by screwing the handle "in" to the desired setting.  If you go past you can't loosen the handle off and expect to get the proper torque.  Unscrew the handle completely and come back "up" to the desired torque setting.

4.  Our torque wrenches are allowed a maximum of + or - 4% tolerance when checking.  When you get to some of the higher torque settings this can be quite a range.  ie. for an 800 inch-pound test the range is 768 to 832 inch-pounds in order to pass.

5.  In order for a wrench to pass it must test accurate 3 times in a row at each setting tested.  We normally test at 20%, 40%, 60%, 80% of the max. rating for the wrench.

6.  Torque wrench accuracy diminishes greatly at the extreme ends of its range.  ie.  Don't use a 0-800 inch-pound torque wrench to torque a bolt to 800 inch-pounds.  Use a wrench big enough so that the torque you are trying to get falls somewhere in the middle of the wrench's range.


Working on aircraft we torque some pretty important pieces.   Propellers, landing gear, engine mounts, crankcase halves, etc.   You definitely want an accurate torque wrench for these jobs.  

Most wrenches either read consistently high or low.  Occasionally I've seen a couple that will test both high and low.  The scary part is if you have a wrench that is reading consistently high but still passes.  You run the risk of overstressing a fastener and possibly creating an accident .  Especially if you are torquing something to the maximum end of a specific range.  The opposite is also true if the wrench is reading low and a critical part is left "loose".

This is a really good thread and a good idea for people doing their own work to get their wrenches checked.  I find them out of whack all the time.

[Mark(The Miser)UK]

I've wondered about the accuracy of my torque wrenches, I was going to make a tester myself.

  1 foot lever with a 50 pound weight on the end that has an old socket welded to it so I can hook the wrench up to it. Put a 3" extension on the wrench then hook it up to the "tester", then you need to place the extention on say the edge of a 2X4/top of a railing so your tester is rotating around a point that is 1' from your weight. Then pick up the weight with the 1' lever in the horizontal position. a 12" extension would be better to you could use your other hand to control it. Then adjust the wrench a pound at a time till it clicks, hopefully you're looking at 50 when it does click.
 [/shadetreemechanic]

[/size]

This is the kind of simple callibration method I'd do.

 Very good points made from the previous posting naturally as someone in the field...

An even easier way I've just thought of...
In my house I have an old set Salter bathroom scales that weigh in lb up to 20 stone. Everyone in my family has one of these thanks to my mother who had one when we were all kids. I have tested these with 1/2 cwt weights and they are accurate to within a lb over most of their range. [Inside is a section of calibrated iron 'I' beam that is bent almost imperceptibly by our weight.] Why not attach  a  1ft lever onto the torque wrench and push down on the scales rest tip of horizontal 1ft lever on a raised wooden block. Whole range  of calibration can thus be checked. :idea:

[Duster 5.9]

why not just clamp the working end in a vise, then hook a scale (fish weighing scale) to the handle and pull watch to see when it clicks off at what lbs

[zukgod1]

why not just clamp the working end in a vise, then hook a scale (fish weighing scale) to the handle and pull watch to see when it clicks off at what lbs

I guess if ya had one of those way nice digital scales this would be cool..

Sounds good anyway..