Torque wrench accuracy

Stan in Oly, WA · May 15, 2017

I need to change a valve cover gasket. I have an old (but little used) beam style torque wrench. I know how to check the accuracy of a torque wrench, but I started wondering how much difference it would make in this situation if it was off by even as much as 25%. If I tighten the bolts until I encounter resistance, then finish each one with the torque wrench to the specified torque, isn't it going to be more important that the bolts are all the same then that they're at a specific amount of foot pounds, as long as they're in the general desired range?

Stan

Steve in VA · May 15, 2017

I think precision is more important than accuracy in this situation.

Steve@Advance · May 15, 2017

You'll be fine with the wrench as it is.

Just bring it down evenly, keep going around until they all read close to the same.

Most important is the surfaces are clean and dry. If it's a sheet metal cover, flatten the holes from the back side so it will pull down evenly.

I've never used a torque wrench on a valve cover, just done it by feel.

Stan in Oly, WA · May 15, 2017

Steve, I think I understand what you mean, but I'm not absolutely sure. Do you mean that it's more important that all the bolts be tightened to the same amount of torque than that the amount of torque be exactly a specific figure? Interesting. I understood the concept from other contexts, but I doubt that I ever took the time to consider the difference in meaning of the two words. Thanks.

Stan

Steve@Advance · May 15, 2017

Well...

You can't go wrong torquing them to a factory spec, if you have that spec.

By doing that, theoretically they will all end up with the same torque.

I don't know what you are working on, the size or type bolt, aluminum or steel...

Or your level of confidence to know the limits of a bolt's strength, or the "is this too lose?, is this too tight?" feel that comes from experience.

I can see using a torque spec if it is a high tech engine, aluminum cover, cam seals involved, etc.

But if it's just a sheet metal cover with a cork gasket, it's not that critical.

Guess I still haven't answered the question. LOL But best to bring it down in steps, start the bolts, finger tight, snug with a wrench, around again a little tighter, then finish to the final tightness.

Hope this helps!

Steve in VA · May 15, 2017

Stan,
Yes, you are right on target. It's a flashback to my nuclear days and instrumentation. As a shooting example, a tight cluster of shots would show precision since the result is reproducible but, they may all be clustered in one corner of the target independent of your aim and therefore have no accuracy. If a system has precision then you can always adjust or calibrate for accuracy but, if you have no precision to begin with, you'll never get accuracy.

So, yes, in my opinion all the fasteners should have as close to the same torque as possible and that's most important since you would avoid distorting the cover.

guido · May 15, 2017

Hello Stan in Oly WA,

Use a 1/4" drive and snug them up with one hand, good as torqued. Your beam type torque wrench is still accurate and will stay calibrated longer then a click type torque wrench.

Guido.

504 · May 15, 2017

A beam wrench is always accurate, just reset the pointer to O.

Stan in Oly, WA · May 15, 2017

Thanks, everyone. Good information and advice here, as usual.

Torque wrench accuracy

Stan in Oly, WA

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Steve in VA

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Steve@Advance

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Stan in Oly, WA

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Steve@Advance

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Steve in VA

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guido

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504

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Stan in Oly, WA

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