JTIS lists torque values as a range. For example: Secondary timing chain tensioner to cylinder 10-14.

What does that mean? I have heard that it means a brand new bolt is torqued to 14 nM and if you are reusing an old bolt you torque to 10 nM.

I just want to confirm this understanding, or is this completely wrong?

I plan on replacing my timing chain tensioners on my 2002 XRK and I want to make sure that I retorque everything correctly.

Thanks in advance.

 

You are right lawnerd but IIRC the numbers are listed the other way round, in any case the higher value is for the new bolt.

 

lawnerd, being someone that has received more training on torquing than I care to admit to, what it means, and how to calculate what a bolt should be torqued to, I will give you a little insight to this question.

First off, the new bolt to the higher value and a used bolt to a lower value is an old tale. They give you a range so that you don't wonder if you under/over torqued something. If I told you it needed to be torqued to 70 ft-lbs and you torqued it to 71 ft-lbs, did you over torque it? By numbers, yes you did. In reality, all is good.

In short, the range is normally based on a minimum and maximum condition. In a lot of cases the minimum is based on providing enough friction to the bolt head that under normal use, it won't back itself out. In some other conditions, it may be enough clamping force (the force that holds two things together) to overcome system pressure (this is normally the case with things like flat face flanges in the industrial world). The maximum is based on a combination of the stresses the fastener will see during normal use and the stress induced into the bolt due to the clamping force (this value must always remain below the tensile stress, else the bolt will break). In a lot of cases, the engineer is not going to push the bolt to its limit, but instead may only take it to say 75% of its tensile limit. That way, should he be off in his calculations or the bolt sees more stress due to say an abnormal condition, things keep themselves together.

Where torquing can become an interesting tight rope walk is when you start mixing different kinds of materials together (using a grade 5 bolt where a grade 8 was originally called out for) or using a different kind of lubricant when assembling the joint (or not using one at all). These all affect how much stress is placed on the bolt. You start messing with different materials, they can dramatically change how a joint will stay together.

I am being very simplistic here as you can write volumes on the various effects and there are charts upon charts of using a certain material in the bolt, with a certain material in the nut, using a given lubricant, using ...... Lots of variables.

I work around things that we have to torque to inch-ounces all the way to millions of foot-pounds. Gotta love something that you torque by putting a heating rod into it, tightening it slightly and then removing the heating rod to make it go to the ungodly torques.

Believe it or not, every time you tighten a bolt, it physically gets longer. We are talking on the scale of 0.001 inches or the like for a 4 inch bolt. But, using very sensitive test equipment, you can figure out how much stress the bolt is under and if you know that a given material will stretch by a given amount as it reaches its tensile stress point, you can see how much of a safety margin you have. This is why if you tighten and loosen a bolt numerous time, it will eventually fail. Every time you stretch it, you are breaking part of the internal structure of the bolts.

If you want to know more, let me know. I can go into more detail should you want.