Torque wrench accuracy

[boatzo]

Realistically,for some one who lives in the middle of no where, how much can I rely on the manufacturer's calibration of the Harbor Freight click torque wrench? I have no means here to check the accuracy.

 

Are my wheels or calipers going to fall off

[dirtrider]

Hi Bill

 

You just never know.

 

I have seen some of those cheapies pretty close and others a long way out. If you have access to a beam type torque wrench just couple them together and see where the HF stands.

Very seldom do you see a beam type torque wrench off very far as the bending properties of the beam is determined by material thickness and shape. As long as the scale is correct and the needle centered then the beam wrenches are usually fairly close no matter what.

 

On the clickers those can be easily damaged by over stressing, or rough treatment in their storage or use, and can be skewed by not relaxing the spring tension while stored.

 

[Selden]

I've been told that, when new, they are at least within +-5%, which is close enough. Always store with the dial set to its lowest position. But, without access to accurate testing equipment, you just have to go on faith.

 

Same thing for tire pressure gauges. How do you know it's accurate? In my experience, I have seen substantially different readings with analog gauges (i.e., pen, dial), but my digital pressure gauges have always given me identical readings, so I assume they are accurate.

[rad]

I have used beam ones for so many years that I don't completely trust my clickers. What I do, I set the clicker, then I test it by closing it in my bench vise and seeing where, by feel, it clicks. I trust my “calibrated wrist wrench” to alert me if something is way off. I then torque the fastener.

 

BTW, I never trust anything from Harbor Freight

 

 

[SageRider]

Interesting self calibration link...

[11101110]

Interesting self calibration link...

 

Very nice. Just remember that clickers aren't always linear. I have a very small clicker from work that is dead nuts on at mid scale (8 Nm quess why I gave it a home) but is out of cal in opposite directions either side of mid scale. I know the guy in our company's calibration shop so my wrenches get a check every two or three years. none have varied much since I have had them. If you store them with the tension released and only use them occasionally you don't need yearly cal checks. Typically the wrenches at work deviate from manufacturer's spec at the very top or bottom of their ranges.

[SageRider]

Yep.

On the clickers I am used to, the bottom 20% accuracy is unspecified, so I would want 3 weights:

20% range, 50-60% range, and 100% range.

[Peter Parts]

As I have argued elsewhere, the clickers are unsuitable for shade-tree wrenches because they reduce the experience of torquing and learning to become a masterful wrench into a "binary digital" moment.

 

I'm surprised to see wise people saying good things about torsion beam models. Mine are spot-on when playing tug-of-war with a lab calibrated clicker.

 

Ben

 

Footnote: critical that torque wrenches be reasonably accurate. But tire air pressure is awfully relative to the rider; in that case, accuracy is not important but it is important that you always check using your own and the very same gauge.

[Albert]

Interesting self calibration link...

 

Just remember, all you space travelers, this technique will only work while you're on the Earth (or a planet with similar gravity).

[SageRider]

Interesting self calibration link...

 

Just remember, all you space travelers, this technique will only work while you're on the Earth (or a planet with similar gravity).

And, of course, to be truly accurate the weights need to be calibrated............

[Dan M]

Interesting self calibration link...

 

Just remember, all you space travelers, this technique will only work while you're on the Earth (or a planet with similar gravity).

And, of course, to be truly accurate the weights need to be calibrated............

 

As does the scale you are checking the weights with...............

[SageRider]

As does the scale you are checking the weights with...............

As does the standard used to calibrate the scale.....

And on and on......

[Mrs. Caddis]

Jeez, maybe I'll just take ours to NIST (National Institute of Standards and Technology), it is not far from Kevin's office!

[11101110]

Interesting self calibration link...

 

Just remember, all you space travelers, this technique will only work while you're on the Earth (or a planet with similar gravity).

And, of course, to be truly accurate the weights need to be calibrated............

 

HAHA. Our cal shop actually has calibrated weights. And if you live in an area with a lot more earth underneath you your mass will weigh more. Some of the stranger things that get calibrated at work are hammers and crimp tools.

[SageRider]

Crimp tools often are calibrated for correct crimping pressure, but hammers???!!! that's interesting....

[boatzo]

Thanks all for all the input. One thing that I hadn't considered was leaving the click wrench in a tensioned condition. I just checked the rear wheel bolts on my LT and guess where the wrench was left, almost to the top. I am going to my shop and relieve it as soon as I finish this post.

 

I have an old beam type wrench that I use to tension my saw mill band blade. I will check that against the clicker as Dirt Rider suggests, to see what I get. Seldon says + or - 5% and that makes sense. I don't think I need the NIST accuracy. The procedure Sage listed is interesting, but the linear accuracy of the clicker would mean a lot of different (maybe only 4 or 5) weights and I don't have anything other than a bathroom scales to weigh the weights.

 

After reading all the posts and thinking about this, I came up with one idea that may have merit. I have a friend that has an auto repair business and several times whilst visiting there, the Snap-On rep came in and we have had some nice chats. Even bought a few tools from him. I am going to ask him if he has anything to calibrate the clicker.(I Don't think I can afford his wrench.) He has a neat air conditioned mobile facility that he travels in and has almost everything known to man in there (he surely must be able to calibrate a clicker).

 

Thanks again all for the input, I think in the meantime I will invest in a better instrument than the Harbor Freight.

[garr2]

A combination of inexperience in using a torque wrench and blind faith in its accuracy taught me a lesson. A torque wrench (even one with a stated accuracy of +/- 4%) is not accurate in the bottom 20% of its range. i.e. I would not now use a torque wrench rated to say a maximum of 100Nm to torque down anything under 20Nm. I have an crush washer that is almost transparent in places to remind me of my folly.

[boatzo]

Welcome to the forum Garr, you make a very good point. I think that one should have at least 2 and possibly 3 different range T/Ws in the tool list.

 

BTW, please fill out your profile and we hope to hear a lot more from you.

[Peter Parts]

Think statistically. Do the mano-a-mano arm-wrestle with three torque wrenches. No need to find a lab calibrated torque wrench as a standard.

 

People complain (incorrectly) that you can't tune with dual vacuum gauges because cheap ones are inaccurate. All you need to do is buy three and return the one off by the most (or bring a multi-tee and MityVac to the store with you).

 

Ben

[boatzo]

I just checked my CLICK torque wrench against my old BEAM type wrench and found the CLICK to be 5 ft lbs low across a range of 15 fp to 80 fp. Looks fairly linear. I don't know if it can be calibrated, but for the time being I have a piece of masking tape on it saying to ADD 5 FT LBS to the settings.