Confused About Torque Values

[Squiggle Dog]

I've been searching the internet for answers and have given up. All I get is irrelevant information. My question is, what does it mean when a service manual says the torque value for a bolt is 75-85 ft-lbs? Does that mean 75 ft-lbs? 85? Somewhere in between? Tighten it to 75 and then tighten it to 85?

I'm working on an old Ford truck and almost every torque value they give has two numbers (30-35, 12-15, 45-50, 100-110, etc.). I want to make sure I understand torque values before I mess up something.

[t walgamuth]

Anything between and including the values is desired.

[Mike D]

As noted by Tom.

https://www.youtube.com/watch?v=iX3kxAA2L4Q

[Squiggle Dog]

Thanks for the responses. Hmmm... but how does one determine which number to use? Just whatever one feels like at the moment? It doesn't seem very exact.

[Diseasel300]

It's the difference between having standards and "that'll do". Ideally the torque value would have ONE number - the target torque value. Obviously this isn't a perfect world, so it will have variance when actually tightened. When presented with a "range" of acceptable values, I generally shoot for the middle of the range as my target. Right? Wrong? Who cares, they couldn't be bothered to give me a proper value to aim for. "That'll do".

[dieselmania]

Add to that the fact that the torque wrench is not equally accurate throughout it's entire range. It is better to have several torque wrenches of different ranges vs a "one size fits all". A wrench with a 0-300 LB range nay not be too accurate a 12 ft lbs. Also add the fact that many torque wrenches are not regularly calibrated.

[Squiggle Dog]

Hmmm, I guess that's the difference between Ford and Mercedes.

Also, I have three torque wrenches for different ranges.

[Kestas]

Realize that torque is a guide to achieve a certain clamp load. Rusty or contaminated threads will increase the necessary torque, and lubricants, such an antiseize, will decrease the necessary torque. The torque range may allow the mechannic to judge which torque is appropriate for the moment.

[t walgamuth]

I'd pick a middle value and try to make all the bolts in the pattern match. No need to over think it. They made a range because hitting an exact number on a traditional torque wrench is not so easy. If you have a digital you can pick one number.

[optimusprime]

Good one TW . The centre of the value is a good guide .

[tangofox007]

Originally Posted by Squiggle Dog

Tighten it to 75 and then tighten it to 85?

That option doesn't work well. Small changes in torque cannot be made incrementally. If the fastener is at 75 and you want 85, loosen and start over.

There is a lot more to using a torque wrench that knowing how to set the clicker. A lot of the tecniques that I see leave me wondering why the torque wrench even came out of the tool box.

[Simpler=Better]

Originally Posted by tangofox007

That option doesn't work well. Small changes in torque cannot be made incrementally. If the fastener is at 75 and you want 85, loosen and start over.

There is a lot more to using a torque wrench that knowing how to set the clicker. A lot of the tecniques that I see leave me wondering why the torque wrench even came out of the tool box.

I like to tigheten it as fast as I can, with a pipe on the end to amplify the click noise

[Squiggle Dog]

Originally Posted by Simpler=Better

I like to tigheten it as fast as I can, with a pipe on the end to amplify the click noise

I've got torque wrench technique down pretty well as I've studied all the tips before. But, I sure could not find information anywhere on what it means when it shows a range. I also interpreted it as Kestas does, where I've torqued bolts with rusty and contaminated threads higher than ones with lubrication. But, I wasn't sure if this was correct.

When I attached the flex plate onto the engine, I went into the middle of the 75-85 range because even though the threads were clean, I put blue thread locker on the threads, and the bolt head surface of the mounting plate was rough and would help hold the bolts into place. Plus, they were the original bolts from 1959/1960 and I didn't want to shear them.

I store my torque wrenches at nearly 0, handle them carefully, and use them with my hand on the handle and do a smooth, steady motion until it clicks, after having the bolts just snug.

Thanks for the insights, everyone. I wanted to make sure that I understood the procedure and that it wasn't anything goofy like torquing to spec and then 90 degrees past the torque like they make you do on Mercedes flex plate bolts.

[Simpler=Better]

Nope, nothing goofy on Fjords. I've even been known to just apply bolts by feel(gasp)!

[moon161]

Originally Posted by Simpler=Better

Nope, nothing goofy on Fjords. I've even been known to just apply bolts by feel(gasp)!

This is me forgetting I don't have pearls to clutch: