All this talk about torque values . .

. . . about the recent threads on torque values got me asking “How many of these guys have a calibrated torque wrench”. I have one – but “calibrated”. NOT lately? I am going to embark on a (near?) total restoration of my SIII in a matter of months.

Hmmm . . … . . got me thinking. I picked up a Snap-On 3/8" torque from eBay years (decades??) ago. It has sat in my toolbox un-used while I finished a stint in the Army and did Def Contracting work in AFG and then some more years.

So I found a test lab in the Springs and dropped off my wrench. Three days and $33.50 later: the Certificate of Calibration says “Calibrated to +/-4% of setting”. I was expecting 2%. So I asked the gal at the counter who said 4% was about as good as it gets. I assume she meant for a torque wrench clunking around in a tool box. I suspect the standards are higher in certain industries with wrenches much more expensive than my eBay purchase.

The cert references a couple Mil Stds and TOs but (and here is my question), also says “Calibrated to at least a 4:1 calibrated ratio.” What is that? I Googled the phrase but am still in the dark. Anyone simplify this for a guy with a Crim Just BS?

maybe this helps.

For your purposes, +-4% is **entirely accurate enough.

It’s a Jaguar, not an aeroplane…!.

I calibrated my 1970s Sears Craftsman “Click” torque wrench by hanging 60 lbs of weight off it at the handle, calculating what the effective weight was at 12 inches, and then adjusting wrench so it just clicked when the weight was slowly hung at that point.

Kindof like adjusting the points on an SU fuel pump so they just click over, and then screwing in diaphragm 2/3 turn!

Dennis 69 OTS

Snap-On dealer trucks sometimes offer torque wrench calibration service on the spot. They also have facilities to conduct off-truck calibration. No affiliation with Snap-On/BluePoint.
It’s interesting watching the 1960 Jaguar factory video as workers assemble various parts/components and mount items to a production line vehicle. One segment shows a worker attaching a steering wheel using a T-nut driver to “torque” the wheel nut. Calibrated elbow? I’m sure the Jaguar ROM has a specific torque value for that nut ! !
Another segment show a worker pounding in cast iron tappet liners into a freshly heated head. Square? So, use some good old common sense when fretting about certain manual torque settings. A calibrated torque wrench should be good for 1,000 “torque” operations or 1 year before requiring re-calibration. Engine components should always be fitted per ROM torque values. Other fasteners not listed via standard size torque values.

Happy Trails,

Don’t let the Old Man in…

I hooked my 40+ year old Craftsman beam TW to my brand new Craftsman dial handle TW. Strangely, the new one clicked when my beat up torsion beam hit the same value.
Are they both “calibrated” now?
I think most folks over-torque fasteners. I know I do.
Steel fasteners in aluminum is why most of us ham fisted mechanics need a TW.
Can you imagine how high repairs would be if everyone used a TW for everything?
Mission critical only. Tip: choke up on your ratchets! Your nuts are tighter than you think :stuck_out_tongue_winking_eye:

I wish I could get a supply of spark plug crush gaskets.
I suspect I over torque sparkplugs if the spark plug crush gasket is already crushed.
I live in Vancouver Canada and can’t source them.
Dennis 69 OTS

I think these would do the trick:

Also, why the Brits ended up with the B-O-P 215 engine.


John – that is exactly the web-site I found with google.
I’ve read it twice and an still prepared to copy/paste it paragraph by paragraph onto Google translator from Greek into English. Still no bueno.
Although based on Paul’s comment, it don’t seem to matter much; good enough is good enough.

I was hoping you would understand it and explain it to me. :grin:

From what I could see it referred to test procedures that were either 4 times or 10 times finer than the margin of error of the instrument being calibrated. If a torque wrench offered an accuracy of ± 2% a 4 times test procedure was repeatable ± .5%.

Score a point for Bing search vs. Google - the 1st hit is this:

Which you kind of think the big leader in search would have come up with early in the list.

I think “accuracy ratio” means the target accuracy of the tested tool divided by the accuracy of the calibrating tool. If the wrench, for example, had a 4% target, a calibration tool of 1% would yield a 4:1 ratio.

As the wiki article states, getting higher ratios is tougher because the calibrated tool and the calilbration tools are closer in performance than ever before. I would guess it’s hard to get a torque wrench calibrator device that’s accurate to .4%, which would be needed for a 10:1 ratio, or a tighter tolerance than 4%.

I took my Craftsman click type wrench purchased 25+ years ago in for calibration 2 years ago and it measured out fine, no adjustments needed. I guess setting to “0” after every use paid off…



When I first bought my Snap-On clicker, back in the early 80s, I was cautioned to always set it to zero, after each use.

Maybe I’ll take it to a Snap-On dealer and have them check it, just for giggles. I’ll wager it’s still plenty good enough.

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[quote=“Wiggles, post:13, topic:386575”]
s, I was cautioned to always set it to zero, after each use.
Yeah that^

I may be fooling myself but I use my ‘craftsman beam’ torque wrench to calibrate my ‘craftsman clicker’ torque wrench. I always set the clicker back to zero when I’m done but mine seem to read low compared to the beam wrench which I have assumed, perhaps incorrectly, are more accurate than the clicker style torque wrenches.

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Either/both getcha eithin 2-4%?

The doctor sez, take an aspirin… yer golden!


With TW I work on the principle that the value to be used is somewhere in the middle 1/3rd of the TW’s range. To this end I use a 1/4 drive unit for torques under 20 ft/lb (eg M6 bolts into alloy @ ~7 ft/lb, dont squash the gasket), 3/8 drive for under 50 ft/lb (M8 bolts at 15 ft/lb) and a 24" long 1/2" drive TW for lug nuts (70 ft/lb, easy as) to front crank bolt (210 ft/lb, some effort required). If I cant use a TW I try to approach low torque fixings with fresh hands that have NOT recently been used on high torque fixings, as this tends to reduce sensitivity.

It’s not really necessary for the torque wrench to be 100% accurate. It;s main function is the ensure all the associated bolts/nuts are torqued to the same value.

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What a novel idea… torquing lug nuts.


“What a novel idea… torquing lug nuts.”
Three reasons I do this - I think its a good idea on alloy wheels, my 24" TW 1/2 drive makes the effort trivial, and the 928 has alloy lug nuts - its become automatic now. Anybody here experienced a problem undoing a nut after a tyre shop has done the, up with a rattle gun? Friend of mine had to give up changing a wheel with make supplied wrench and call the auto club because he couldnt move the nut - recently fitted new tyre.

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