Choosing a Torque Wrench

Story and Photography by J.G. Pasterjak

That click–so familiar to anyone who’s spent time getting their hands dirty in the garage. That satisfying little pulse in your hand that signals a job well done. It’s a welcome piece of audible and tactile feedback to enthusiasts everywhere.

But how good is your torque wrench? And how much should you trust it? …

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I'm using a 1/2 inch Craftsman click to torque wrench that I bought new in 1992 for a head swap on my 302 Ford. I also have the smaller inch-pound, 3/8 inch version of the same wrench, but it's hardly ever been used.

I don't do much wrenching any more, so I only use it for the frequent wheel changes on my ES Miata (up to several times per month).

I don't know how off my actual torque values are, especially with an adaptor for the 3/8 inch socket that I use, but I figure that at least they're probably all consistent when I tighten down my wheel nuts.

I asked a Snap On driver/dealer about calibration of my torque wrench, he would hardly speak to me.

I have one of the hammer store electric adaptors, but have never used it for anything.

I'd like to have these tested, but not sure how to proceed. I looked into sending them off for calibration several years ago, but it was pretty costly, so I didn't follow through. Suggestions?

BTW, it's pretty sad that Craftsman is so dead that they weren't even in the test.

I have a HF 1/2 in torque wrench I got in the 80s (1980s). I've used it most often for wheels (at home and at tracks) but have done engines too. I've had the calibration checked a few times and it has never varied by much. It has been done by these guys who are all over the US IIRC.

Correction - just in the west

https://www.nationalcalibration.com/w/

I'll honestly click a $20 HF torque wrench on the most expensive thing you can find me. I think people's trust of higher-priced torque wrenches and distrust of cheaper ones are EQUALLY unfounded. I don't trust ANY of them to be any better than 5% anyway. And that's..completely adequate. It's more like $10 with a coupon, too! 

Vigo's post does bring up a relevant question: is within 5% adequate?

I used that same Craftsman torque wrench for an engine swap and a couple of head swaps on the same car later on.

There's lots of variables when it comes to blown head gaskets, but I went through a few on the next engine.

Floating Doc said:

Vigo's post does bring up a relevant question: is within 5% adequate?

Good question

https://www.pcsllctn.com/5-reasons-why-your-torque-wrench-needs-to-be-calibrated/ 

Most tool trucks have a self service torque wrench testers on board. If you know any one who works at a place they regularly stop they should be able to test them for you. 

I had the trusty Harbor Freight 1/2" drive torque wrench for years. After I had 3 head gaskets fail on my mini i tested it on the Snap-on truck and when set to 100ft/lbs it was clicking at 70.  I chucked it in the scrap metal bin.

I suppose I should replace it but I just borrow the shop techangle for now.

In a previous life I was a nuclear mechanic for the US Navy.  As part of my continuing education, I went to instrument and tool calibration school.  I also did torque testing for our torque wrenches and torqued a few bolts and nuts in my day.  The nuclear Navy has a huge distrust of click type (micrometer) torque wrenches and strongly prefers dial indicating ones or even beam types.

Other advice is to always use a wrench so that you torque value falls between 15-85% of the wrenches range.  It also needs a valid calibration sticker.  
 

And yes 5% is fine.  I'd be more worried about calibration than brand.  A calibrated cheapo is better than an uncalibrated expensive tool.  

The only torque wrenches I've ever bought that had calibration data are the two CDI torque wrenches I got last year.  I shoukd probably get a torque tester or find one near me that I can use on e a year or so.

is within 5% adequate?

Possibly a more relevant question. Do you think manufacturers would subject themselves to the ludicrous suffering they would endure if they built pretty much any fastened assembly within 5% torque of failure and then sent it out into the world of real life dealership techs?

I'm sure there are plenty of cases when 5% isn't enough. But they don't pay auto techs enough for 5% to not be enough. 

In reply to Vigo :

I understand what you are saying but +/- 5% of torque is way different than a 5% failure rate.  A torque rating is specified in order to generate a sufficient clamping force.  It's also spec'd knowing the fastener can take all of that and then some by a pre determined safety factor.  In typical mechanical engineering that safety factor is 2.0, or 100% more than the designed load of the mechanical item.  Civil engineering may use even higher safety factors.  In the previous case, the problem arose when the torque wrench was reading 30% low.  That sounds pretty legitimate to me. 

Getting the exact torque also depends on cleanliness, specified lubrication, etc.  How many people do you know that chase threads and use the correct lubricant before torquing fasteners?  This alone can cause for more than +/- 5% torque.  I don't know many auto techs that get paid enough to go to this kind of trouble.  Some do, but most do not. 

For example most lug nuts are torqued 75-100 ft-lb in my experience but that's a clean stud and fresh lug nut.  How many people do you see torquing beat up rusty studs with mangled nuts?  I don't chase threads myself, but do check them for cleanliness and keep wire brushes handy.  If I'm torquing head bolts though, I go to a lot of trouble to chase, clean threads, and use specified lubricant (in some cases it is none or dry).  In the nuclear navy they had a special lubricant that was used on almost all fasteners and required to get the correct spec.  It also prevented galling.  Once galling of your fasteners starts, you will never get to the correct clamping load no matter how well your torque wrench is calibrated. 

I actually got irritated during study for my mechanical engineering degree, because so many engineers don't understand nuts and bolts..... If you want to be beat down with the details the mechanical engineer's handbook  is heavy reading, but good reading. 

Needless to say there is a lot more to the puzzle than having a torque wrench and getting a torque reading within plus or minus a given percentage on that wrench.  Thanks goodness most stuff is just overdesigned to compensate. 

I have a HF 3/8 and 1/2 clickers, a CDI flex 3/8, and Quinn digital 1/2. 

The quinn is made by Eclatorq same as the Kobalt, made in Taiwan and I like it. Also does angle if you need it to. 

All of em except the quinn have rebuilt motors with zero problems. 

In reply to AnthonyGS :

I never use a tap to chase threads unless I'm making a new hole. I keep a metric set of Lang Thread restorers as that is the proper tool for cleaning up boogered threads

ChrisLS8 said:

In reply to AnthonyGS :

I never use a tap to chase threads unless I'm making a new hole. I keep a metric set of Lang Thread restorers as that is the proper tool for cleaning up boogered threads

I agree thread chasers are far softer than taps.  They should be used to remove dirt grime and old sealant, etc. If you have a damaged thread(s) other tools come into play.

Then you have to figure out the correct lube for the given torque spec which seems to be rarely published or considered.   

Floating Doc said:

Vigo's post does bring up a relevant question: is within 5% adequate?

When I worked as an A&P on an Air Force contract, all of our tech data stated +/- 3%. Everything (including the 6 inch scales one time) that was used to measure tolerances went out every 2 years for calibration and we had to check the cal sticker everytime the tool was used.

Our family friend is a matco dealer, had him test all mine and all where within 4%. 

Pretty impressive for a old ass matco, new snappy, Pittsburgh, icon, and some no names from junkyard. 

He told us he rarly sees them out of spec. 

In reply to AnthonyGS :

I did my apprenticeship as a civilian contractor on Nuclear Subs in early 80's. Used a click type a few times, but COUNTLESS Dial Torque Wrenches! Rebuild my first engine with a way cheap Sears beam and pointer... don't even know hou to explain how cheesy one is! But it did the job. Good mechanical practice and skill of the craft goes a long way, and I learned very little of that from degreed engineers

03Panther said:

In reply to AnthonyGS :

I did my apprenticeship as a civilian contractor on Nuclear Subs in early 80's. Used a click type a few times, but COUNTLESS Dial Torque Wrenches! Rebuild my first engine with a way cheap Sears beam and pointer... don't even know hou to explain how cheesy one is! But it did the job. Good mechanical practice and skill of the craft goes a long way, and I learned very little of that from degreed engineers

This was the most shocking part of getting my degree.  There is a vast difference between a good mechanic and mechanical engineer.  I spent most of my senior year in the labs actually building and making things work that smart people dreamed up.  

In reply to AnthonyGS :

In the nuclear navy they had a special lubricant that was used on almost all fasteners and required to get the correct spec.

Absolutely. MolyCoat, copper and nickle anti-seize has always been available over the counter, but too few will use it - lots dont know what they are.

The0retical said:

When I worked as an A&P on an Air Force contract, all of our tech data stated +/- 3%. Everything (including the 6 inch scales one time) that was used to measure tolerances went out every 2 years for calibration and we had to check the cal sticker everytime the tool was used.

When I was QC, answering to NRRO, our 6" scale only had to checked before first use. After that it can't change, unless damaged, and then we were expected to destroy and trash it. We couldn't get the position without knowledge, experence and integrity... and yet I can't apply for a job at Ft Rucker, 'cause I don't have a A&P. To work next to people I know, that don't have one, and don't know enough to get one, but have conections..... OK, I'll quit whining now!!!

Torque specs range anyways. I always pick the middle. I've done a lot of work to different cars. Never died. Use a chinaFreight Snapper the whole time. 4% variance on 40-60ft lbs is 1.6-2.4lbs. 

03Panther said:

. and yet I can't apply for a job at Ft Rucker, 'cause I don't have a A&P. To work next to people I know, that don't have one, and don't know enough to get one, but have conections..... OK, I'll quit whining now!!!

Yeah, helps to have connections a Rucker. Have you tried any of the quickie courses to get your A&P? Got mine at a full school, 1 year of night classes and shop time. But I used to teach at one of the quickie schools, NCI in Clarksville, TN. Designed for folks with military aviation experience, just need to learn to translate it to civilian philosophy. 

Another nuclear navy trained calibration guy, specifically on calibrating torque wrenches. 

Hands down a beam type is the most consistent, and typically the toughest to read. I have a fixture somewhere in my shop that I can clamp in a vice, drop my beam type in, and connect my clickers to the bottom.  Cycle the clicker until it clicks while watching the beam on top. Easy, quick cal check. 

In reply to oldopelguy :

I was a sub guy, so we had to learn to do it all.  I went to nuclear mechanic school, chemistry and radiation controls school, taught 114 ton refrigeration school, taught nuclear valve school, taught chemistry and radiation to officers, went to machine tool operator school (lathe and mill), assisted with that class sometimes (needed 1 instructor per 3 students for safety), went to gauge cal school (thermo, pressure, torque), qualified quality assurance inspector (one guy usually does nuclear work and another guy checks it), and just fixed things that broke on the boat.  Oh I also went to fire fighting school up to advanced fire fighting which was a week of putting out fires with busted nozzles, bad extinguishers, ripped hoses, fires starting behind you..... all around you..... Oh that was fun.  Then 9/11 happened and someone decided I needed to be trained by Marines to be a part time MP......  Yes, I'm glad I did it.  Do I recommend it? Not neccessarily....  Did it pay for my Master's degree?  Yep. 

AnthonyGS said:

In reply to oldopelguy :

I was a sub guy, so we had to learn to do it all.  I went to nuclear mechanic school, chemistry and radiation controls school, taught 114 ton refrigeration school, taught nuclear valve school, taught chemistry and radiation to officers, went to machine tool operator school (lathe and mill), assisted with that class sometimes (needed 1 instructor per 3 students for safety), went to gauge cal school (thermo, pressure, torque), qualified quality assurance inspector (one guy usually does nuclear work and another guy checks it), and just fixed things that broke on the boat.  Oh I also went to fire fighting school up to advanced fire fighting which was a week of putting out fires with busted nozzles, bad extinguishers, ripped hoses, fires starting behind you..... all around you..... Oh that was fun.  Then 9/11 happened and someone decided I needed to be trained by Marines to be a part time MP......  Yes, I'm glad I did it.  Do I recommend it? Not neccessarily....  Did it pay for my Master's degree?  Yep. 

 

 

The Navy Nuke Sub program is prolly tougher than anything else I know of. I would not have ben dedicated enough to make it through... so I have HUGH respect for those of you that did! And, thanks for your time, too.

I was Outside Machinist in the Apprentice School... but I had two years of electronics before that... but that was in 79, so I've slept since then! Then 6 years in QC. The Aprentice program at NN ship was better than other programs, but not as intense as yours. I didn't have the chemistry and radiological training you had, and didn't work on valves till I started contracting in 97. But Fisher AOV's became my bread and butter for many years

were you ever in NN ship?

I understand what you are saying but +/- 5% of torque is way different than a 5% failure rate.  A torque rating is specified in order to generate a sufficient clamping force.  It's also spec'd knowing the fastener can take all of that and then some by a pre determined safety factor.  In typical mechanical engineering that safety factor is 2.0, or 100% more than the designed load of the mechanical item.  Civil engineering may use even higher safety factors.  In the previous case, the problem arose when the torque wrench was reading 30% low.  That sounds pretty legitimate to me. 

I was out of town for a week but in reply, I never said failure rate per se. I implied that a manufacturer wouldn't give you a torque spec that would result in broken parts if you went 5% higher. So my point was that 5% accuracy was good enough and everything but your first sentence there seems to be in agreement on that.