Macadoo

I got curious today (and didn't feel like installing the new weatherstripping I bought) so wanted to see how accurate my torque wrenches are. The answer is; not very.
But first I should ask if this is the proper method to test. I weighed the bar bells and box/duct tape on my digital scale for accuracy.

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My bar-style wrench reads 27.5 ft lbs with 21 lbs weight (weights plus box). My ratchet-style (cheapo harbor freight) reads around 24 ft lbs.
I suppose now I have to test my digital scale. I have another at school.

No wonder I've always felt the need to over-tighten when torquing

oldstata

Wow Mac, Here is one for you how do you determin how much torque to add or subtract for extension's when used

( I really do need to know this formula )

coppercutlass

In this area I spend good coin went with a matco torque wrench and I can have it calibrated anytime for 20 bucks. When it cost 325 bucks 20 bucks ain't much lol.

oldstata

Is yours the digital one with does degrees as well ? They are great before I bought the snapin one I got a napa one with out the degree's option it works well and it was like 150 bucks

coppercutlass

I don't trust digital . Just your typical click type tq. Wrench.

Macadoo

$325?! Dude!

coppercutlass

I don't cheap out on tools lol. Over the years (8) my investment in tools and tool box is around 20k. Box alone is 6k but when the tool guy takes 20 a week it makes it easy to swallow that bill . Plus they pay for themselves when you work with them day in and out.

Macadoo

Well yeah, when it's your profession, it makes total sense. I've been known to spend more than 3k on tools and materials for a new sculpture.

So the question that remains is; is my wrench consistently that much off? Can I just choke-up on it to compensate? I mean, it's all about leverage, yes? I may do some research.

coppercutlass

I belive carcraft did this testing a few years back. They said the hft tq. Wrench was worth the value if I remembered right. They also showed how to check at home.

oldstata

Copper, I feel different in digital then you. I personally have both and my digital is used often and checked yearly.

Mac, if memory serves me when checking you check at three different torques to verify. If this is a hobby that you plan to keep loose the HF torque wrench and get a good one, at least a napa or a craftsman will do you better justice.

coppercutlass

Oldstata the reason I don't trust digitial is because its more easy to break. If you drop it . For example if you dropit I personally would get it re calibrated but if the electronics take a dump then its in for repairs. For me its one less thing that can go wrong.

pogo69

I bought a HFT click after reading the car craft test and the HFT wrench is as accurate as my trusty craftsman that I have had for 30 years that has been recalibrated over the years and always zero'd out after use

1970cs

IIRC my MAC half incher cost $300.00 about 15 years ago.

Pat

MDchanic

Once you confirm that your scale is accurate, you should be able to readjust the torque wrench yourself.
Don't ask me how, but I know there's a screw somewhere that'll do it.

- Eric

oldstata

Yes, if you drop it it does need to be calibrated but in truth doesn't the clicker style if dropped several or hard fall as well ? Torque wrench need care no matter witch one you choose.
I have had mine for five years with no problems at all used at least once a week if not more

coppercutlass

Same here . I dropped it once in the 6 years i have had mine had it re calibrated and i dont take chances like that. I was just saying how the digital wrenches have one more sensitive thing that could fail and thats the electronics if it where dropped etc etc. My whole reasoning is its just one more thing i can do with out and one more thing that could go wrong. click type has been around for ever and works just as good and its sweet and simple.

Macadoo

I'm looking in to that. Not that I don't think a $300 wrench is worth it, but for me, it's $300 I could spend on something that needs torquing

coppercutlass

You dont need a 300 dollar one mac .This one imo is a good compromise.

this is the one my matco dealer tried to sell me but i like being able to give my tools to the dealer and have him handle the warranty work.

http://www.tooldiscounter.com/ItemDi...kw=PREC3FR250F

Run to Rund

The most accurate torque wrenches, and those that also stay in calibration "forever" are the beam type where the beam is a spring and a separate pointer is attached to the head. They are also the cheapest.

Macadoo

My beam-style was the furthest off. But it was a yard sale wrench.

MDchanic

.. They can also be used to calibrate the other kind.

- Eric

pogo69

Beam types are fine , I used them before my click in the early 80's and still have a few and they are accurate but mastering them is another story, its easy to over or under pull when your number hits the pointer...way i see it is i'm not working on a space shuttle or exotic aluminums or titanium or composites so being in the ball park with mostly cast iron and steel is fine

MDchanic

Makes me wonder about your scale.

- Eric

Macadoo

Yup, me too. I'm going to check with another scale tomorrow. But I really think it's the bar wrench. My ten pound weights both weighed in pretty close; something like 10 lbs 3 oz.

m371961

I thought the weight had to be 1 foot from the drive center to give a 1- 1 ratio. You didn't mention the distance. Here is how Wiki says to do it. http://www.wikihow.com/Calibrate-a-Torque-Wrench

Macadoo

I didn't measure the distance so I'll do that. I was going by where the instructions said to place your hand when torquing.

Macadoo

Lol, I just finished reading that same article before I saw your post.

Macadoo

This is an interesting "structable", though I don't care for his weight method.

http://www.instructables.com/id/Fixi...renc/?ALLSTEPS

Stevec

I bought a 3/8 drive digital snap on for over $400! Needed it for work but I use it more on my olds than anything else!

MDchanic

Y'know, Duh, that's a good point.

You are not using the torque wrench to tighten bolts, you are measuring the torque applied to the torque wrench, so 50 pounds attached 12" away from the central axis would exert a force of 50 ft/lbs, while 50 pounds attached 24" away would exert a force of 100 ft/lbs.


- Eric

m371961

Yeah, I don't like that either. Another thing to think of is the weight to calibrate at. I wouldn't calibrate or check a 200 lb wrench (max setting) at 20 or 30 lbs.

jensenracing77

We have a very accurate fish scale at work. We test our torque wrenches like this also. We marked our company torque wrenches 12 inches out and just pull down with the fish scale till it clicks. It is not a perfect test but it gives us an idea when something has changed and in need of a calibration. I have a SnapOn Tech wrench and has never been off and never needs adjusted. It is digital and when I test it like this it is dead on all the way through the range. I check it about every year or two. It is easier to test like this than a clicker type. I don't often buy expensive tools but when i buy a torque wrench I always buy Snapon.

Macadoo

Hence pound feet
Funny thing is, the directions put my hand 14 inches from the pivot point. Of course that moves inboard the higher the setting.

Good point. But when I built my engine I think the highest setting was...what? 80 ft lbs? Or the crank bolt, which I don't recall exactly.

Interesting way to do it. Selling tuna on the side?

ELY442

Mine is $800 and its the 1/2" drive. It beeps and vibrates once you reach your settings. It even tells you if you went over or under your torque settings.

Fun71

Exactly. I can tell in the pictures that the weight is further than 12" from the fulcrum point. If you measure that distance (in inches), divide by 12, then multiply by the weight you measured, it might just work out to the value your wrench told you.

71rocket

I shouldn't have opened this thread, now I'll have to go out and test my torque wrenches.

rustyroger

Less engines have torque settings for critical fasteners these days.
Most head bolts are torque-to-yield, with tightening done by turning the heads a specified angle, or a series of angular turns.
Ford (Europe) and some other makes do the same with connecting rod bolts on some engines.

I had my 30 year old Britool torque wrench calibrated a while back, it was accurate to 2%, just as when it was made.

Roger.

Macadoo

Yeah, that was a game changing realization. So I measured out from the center of the pivot and marked the handle (about an inch in front of the grip, depending on the setting). I then ran my test again using 20 lbs and 30 lbs respectively, putting the weight right at the 12" mark. Lo and behold it's within a half pound. So this begs the question; when I use the wrench, should I grasp it at the 12 inch mark? And if so (which I think I should), why is the grip further outboard? I'm curious if you folks with the high-quality wrenches have the grip 12" from the pivot or if the wrench compensates for a longer (breaker) handle.

Ignorance is bliss, isn't it?

MDchanic

No.

The force that you exert in a tangential direction to the rotation axis will vary depending on where you grab the wrench, but the torque applied to the fastener will be the same at the moment the wrench clicks, regardless.
That's the principle of leverage.

If you grab the wrench 24" out, you will exert half the force, but have to pull through twice the arc distance.

If you grab the wrench 6" out, you will have to pull twice as hard, but only half the distance.

The wrench is designed to sense the actual torque you are applying, and not the force you are exerting.

- Eric

MDchanic

To put it a different way: If you didn't have a torque wrench, but only had a spring scale (like for weighing fish), then you would be able to measure the measure the torque by pulling at exactly one foot from the center, with the same force as the number of foot-pounds desired, as measured by the spring scale, but since you do have a torque wrench, all of that is unnecessary.

- Eric