Torque vs Torque turn

[Tim [GA]]

torque specs are listed as either torque to torque turn. I have asked engineer"s why torque turn and they would say it is used because of a defective thread. Then I would ask if the defective thread would effect the initial torque and you get the deer in the headlight look. Is one method better than the other and why. Happy New Year

 

[caseyc]

When you say torque turn do you mean rolling torque? I know rolling torque is used on pinion bearings and such. You can't torque it still because as soon as it turns that value is no longer true...

Casey in SD

 

[Tim [GA]]

To me torque turn is like a spec of 50 ft.lb. and a 90 degree turn. The old JD waterloo engines [thick cylinder heads] use torque turn while the Dubuque engines [ normal thickness or thin head] use torque.

 

[DaninKansas]

Test

 

[caseyc]

Ok, I know what you mean now. Lot of that still around today in automotive and industrial applications.

Casey in SD

 

[JDemaris]

As I understand it - one way is no better then the other IF the proper controls are used with the "torque" method. By "controls" I mean the proper lubricant on the threads to match the torque specs. Torque specs in critical areas are sometimes given different values depending on what type of lubricant is used on the threads and under the head of the bolt.

With the "torque turn" method - having a properly lubricated is not as critical to get the required tension on the "steel spring" bolt.

 

[Steve@Advance]

I see your point, about the bad thread affecting the initial torque, but so would a thick gasket as it was being compressed...

I don't understand the advantage of the "turn to torque" method either. One difference is the "torque to xx ft. lbs" uses lubricated threads, and "torque to xx degrees" calls for dry threads.

Seems to me good, oiled threads would give the desired results, especially in reassembly in the field where "dry" might be impossible to accomplish.

I've used the "torque to xx degrees" method, with dry threads, new bolts (as recommended) and rechecked with a torque wrench. According to the torque chart, I found them to be right on the recommended torque.

My conclusion, if I'm working on something with a reputation for failure, like aluminum cylinder heads, and it's important it doesn't come back (like a paying customer) I follow the factory specs, just to say I did what I was supposed to do...

But if it's my old patched up junk, I'll usually put the old bolts back in and torque them like I always did. So far, so good.

 

[jimg.allentown]

You just described "torque to yield" torque application. In other words, tightening a stretch bolt.
I have been working on automobile and might/medium truck engines for over 45 years, and I am unfamiliar with the "Torque vs Torque turn" difference - whatever that may be.
Normally, when assembling an engine after a repair, bolts are to be clean and lightly lubricated, and torqued to a defined specification.
Many modern engines use "stretch bolts" for critical applications - most commonly head bolts. These bolts are torqued to a specified torque and then turned an additional 90 degrees one or more times. This is called a "torque to yield" bolt. The bolt is actually tightened to its yield point. Apparently this type of bolt maintains more consistent clamping force through the variations in temperature that engines are exposed to. I see them most commonly as head bolts on engines with Aluminum heads on a cast iron block.

 

[JDemaris]

The effects of friction increase as turning-torque increases. So, torque-wrench specs are given with the assumption of a certain amount and type of lubricant on the threads and under the bolt-head. The bolt is just a solid steel spring that is supposed to get stretched to a predetermined amount. Some engineers decided that the "torque-turn" method was more reliable in uncontrolled environments to get the bolt stretched to the proper amount. I.e. "not too little" and "not too much." How true that is - I cannot attest since I don't have a test lab. I DO know that many people just stick the bolts in and crank tight without giving much thought to using the correct lubricant.

I do not believe any BS claims about this having anything to do with damaged threads.

 

[ben brown]

(quoted from post at 16:05:01 12/27/13) The effects of friction increase as turning-torque increases. So, torque-wrench specs are given with the assumption of a certain amount and type of lubricant on the threads and under the bolt-head. The bolt is just a solid steel spring that is supposed to get stretched to a predetermined amount. Some engineers decided that the "torque-turn" method was more reliable in uncontrolled environments to get the bolt stretched to the proper amount. I.e. "not too little" and "not too much." How true that is - I cannot attest since I don't have a test lab. I DO know that many people just stick the bolts in and crank tight without giving much thought to using the correct lubricant.

I do not believe any BS claims about this having anything to do with damaged threads.

my take is this a torque wrench i believe would be more accurate at lower torque just my 2 cents

 

[guido]

Hello Tim (GA),

The torque and turn method is used for a more consistence torque value applied. Having the wrench torque to a lower value, makes the torque wrench error a lot smaller,

Guido.

 

[guido]

Hello jdemaris,

Cummins rear main caps used to be torqued to 300#
Now they are torqued to 150# and turned 30 degrees. I checked with a torque wrench, and the turn method is 300#

Guido.