A bit of a shock - Torque wrench test

Last year I bought 2 new torque wrenches from Proxon one 6 to 30 Nm and the other 20 to 100Nm. I was trying to get a "feel" for 25 Ft/lbs for the crank nuts and then thought I would test the wenches against each other - Woooo The 100 Nm wrench was way out reading 1/3 more than the real torque! So 25 ft/lbs (33 Nm) was actually about 17 ft/lbs. OK, no chance of busting the bolts but I think I have one or two loose heads around! The small one, after playing with some school mathematics and weights, I found to be almost bob on. So this is my reference. I have now calibrated the big wench with some weights at fixed length, so quite happy now.


So moral as usual :-( is check and check again, even if new and a supposedly "quality " product - ha ha! I am just pleased that I have not over torqued/streched anything. Even so, still a really nasty wake up call.

Regards

Re: A bit of a shock - Torgue wrench test

Yes, the maker of quality (here in USA) torque wrenches says not to rely on accuracy below 20% of it's full range. Page 2 here: http://www1.snapon.com/V2/Groups/cmsIND ... ochure.pdf

I'm in the same boat, I have a "grey area" down near 8-20 ft. lbs.

Re: A bit of a shock - Torgue wrench test

I've found the bend bar type torque wrenches the most accurate, the clicker type tend to be in the ball park..

Re: A bit of a shock - Torgue wrench test

I believe it. My buddy Fraser dropped by to show off his new digital readout torque wrench kit. Could be alot more accurate ? Spring pressures in a tool would always be ballpark unless very high quality steels used and of course tested in the factory before leaving it.

Re: A bit of a shock - Torgue wrench test

The top quality torque wrenches come with a calibration certificate. I have a TengTools 210Nm.
Average torque at 40NM = 39.91Nm, at 110Nm = 107.38 and at 210Nm = 215.21Nm. It's a click type wrench, not a beam. Typically you get what you pay for.

Re: A bit of a shock - Torgue wrench test

I bought a new set of crankshaft bolts for my 650 Triumph from a dealer, when I was a kid. When I torqued them up to spec. they broke, and it had nothing to do with the torque wrench. I went back and complained and the guy just mumbled and walked away. He was an ex-factory racer who'd returned to Australia and built his business on his racing reputation.

Re: A bit of a shock - Torgue wrench test

I reagularly have to test everything from 1/4" anchors to 1 1/2" & 2" A-325 & A-490 bolts at work between 500 to 1,500 ft/lbs. I have a skidmore to calibrate & check the bolts, guns etc & now use a 4 times multiplyer & 600lb wrench but years ago we bought a 2,000 lb Snap-on wrench & it was taken very good care of & calibrated often. After only 4 years it could not be calibrated correctly & no one including Snap on would fix it or sell me the parts so I could fix it!! Snap on said " just buy a new one!!" I will never buy another tool from them. And yes, any tourque wrench should be tested before trusting it.

Re: A bit of a shock - Torgue wrench test

Even calibrated ones will eventually read wrong, on the engine assembly tracks at Longbridge all the nut and stud torque wrenches/airtools were calibrated weekly and there were still problems with torque figures at the test area, not all could be put down to operator error (but most were).

Re: A bit of a shock - Torgue wrench test

motoracer8 said:

I've found the bend bar type torque wrenches the most accurate, the clicker type tend to be in the ball park..

Click to expand...

Me too. I build stroker VW engines and use the bar type as the torque values are real low like 15 ft lbs to 26 ft lbs. Too low for a click type plus you get a better feel with a bar type.

Re: A bit of a shock - Torgue wrench test

Gosh darn if you are as logical down to Earth common sense as ole hobot, guess what that implies on all the mis troqued fasteners by fastidious disciplined T-wrench users that look down on the lazy elbow click calibrated wrenchers. Anywho a good part of having such a complex needful Commando is the worship rituals to feel good inside dealing with such fussy fickle fastener torque. Ya do know to take into account the engine and wrench temperature clearances don't ya?

Re: A bit of a shock - Torgue wrench test

hobot said:

Gosh darn if you are as logical down to Earth common sense as ole hobot, guess what that implies on all the mis troqued fasteners by fastidious disciplined T-wrench users that look down on the lazy elbow click calibrated wrenchers. Anywho a good part of having such a complex needful Commando is the worship rituals to feel good inside dealing with such fussy fickle fastener torque. Ya do know to take into account the engine and wrench temperature clearances don't ya?

Click to expand...

And don't forget relative humidity and phase of moon.....just kidding....

Use Nigeldtr calibration technique, or Al-otment's advice to buy certified quality, if +\ - 20 % bothers you.

Slick

If you are really going to use torque wrenches, you need at least three, one for each of the appropriate ranges that you will be measuring. Also, as noted, they need to be certified with a cert slip from the manufacturer that verifies that the particular wrench (by serial number) met the specs when it left the factory. Then, of course, it needs to be checked and re-certified periodically. Buying a wrench that is not certified and/or using a wrench in the incorrect range means you wasted money for a wrench that does you no good at all.

Also…torque settings are meaningless if you don't know whether the torque spec for the fitting is for dry or lubed threads and, if lubed, with what? Using torque specs without knowing that info is a waste of time because the reading could be totally wrong…to the point of fracturing a fastener while the wrench shows it is not yet up to torque. IOW, if a fastener is supposed to be torqued dry and you lube it with engine oil and torque it to X ft Lbs, the actual torque on the fitting will be X + 30% which could fracture the fastener.

Hi, now we are there .........! so what must we (I) do for torquing say an important nut (conrods, or flywheel), use lube ? which kind ? and as we could put some loctite on the threads , the lube and loctite are not the best friends , is the loctite act as a lube (I think it could!), or must we measure the bolts elongation as for the Carillo .........which is not easy peasy!! I am just looking for a second hand Snap-On to replace my old wrench..........

Unless you are prepared to have the wrench calibrated to ensure it is accurate, OR the seller can provide proof that it was recently calibrated, I wouldn't buy a second hand torque wrench (or any new torque wrench that does not come with a factory cert slip - i.e. the common torque wrenches sold in hardware and auto parts stores.

As noted previously, you need to know if the torque specs are dry or lubed and if they are dry and you wish to lube/antisieze/thread-lock, you need to apply the difference involved. Otherwise there is no point in using the torque wrench at all. There are tables available that show the difference in various lubricants. Many factory shop manuals for engines specifically state if the fasteners are to be torqued dry or lubed. I can't recall if the Norton manual does or not - I don't have one here. But other manuals I have do state that and some state dry and others state "clean and lubed with 30 weight engine oil."

Note that calibration is done at a range of settings so you can't just check a wrench by hanging a 20lb weight on a 12" bar and seeing if the wrench shows 20 when it moves that weight. It may be dead-on at that and way off at 40, for example.

In the absence of factory specs you can come up with a reasonable torque setting for fasteners if you know the grade/size/material of the fastener - there are tables for that. OTOH, people have been assembling things for years without torque wrenches with no problems…

FWIW, keep in mind the old story about determining torque settings - originally, to determine the torque settings for engine fasteners, allegedly a company had their ace mechanic assemble an engine. They gave him a torque wrench but he did not pay any attention to the readings, he just tightened the fasteners by feel. A lackey read off the readings as the mech assembled the engine. They then published the readings as the "specs" for the engine.

As a mechanic most of my life, one can attain a feel for certain fasteners, the elbow torque wrench is all that is needed.

But for rod nuts and bolts, head bolts and studs, you should use a accurate torque wrench. Many rod bolts are checked by bolt stretch and should be used only once. Cylinder head bolts and studs are stressed with a torque angle gauge.

I worked on Porsches for many years, the air cooled ones would break cylinder studs if not torqued correctly.

I have several torque wrenches and they do need to be checked form time to time.

My two cents.
I recently watched a Lunmad vid on Utube where he was installing pistons with new bearings. He was not using a torque wrench as he said "why bother, they aren't accurate anyways"
In the comments section, he got beat up for not using one.
Guess he was right

If ya really care to apply the effort it takes to do rod bolts and crank bolts right you measure the stretch and can use t-wrench to measure how much torque to get there or not. The others like head and case clampers I think waste of time effort as they are pretty robust and basically just need cranking on till stays sealed, which can be done by feel or t-wrench as you feel best about but the end result is the same there. My like new clicker wrench showed 27-28 lb to get rod bolts to .006" but who counting eh.