Hello Mr Guest,

Here's a link to a relevant spec sheet: http://www.sandmeyersteel.com/images/2205-Spec-Sheet.pdf

Is this a critical application that you are designing? Is it important to apply the proper bolt load? If so (and with all due respect), you are going about this incorrectly. I would suggest that you initially determine the degree of clamp load required to ensure integrity of the joint (refer to the spec sheet to see if the material is suitable). Indicate this clamp load as your primary tightening specification rather than torque.

If you specify torque, you risk having your equipment fail - even if the installers apply the "proper torque".

You need to ensure proper clamp load, correct? Torque is not a metric that defines clamp load. It's only a measurement of the resistance felt when trying to tighten a nut or bolt. The underlying issue is that you cannot predict what the actual Friction Coefficient will be during assembly; there are simply too many unknown variables! You may "guess" that it will be say, 0.11 but, what if it's actually 0.16? In that case, your torque spec will result in bolts that are too loose. On the other hand, if you assume that the K Factor will be .11 but it's really 0.09, the bolts or the flange may yield. In either case, the installer would be applying the same specified torque value that you had specified.

To limit your exposure to risk and to prevent failure of your design, specify bolt load. However, since assemblers and installers usually don't know what to make of these values, yes, go ahead and specify a torque value but, indicate that it is merely a target based on a certain K-Factor. This is what some refer to as CYA or, "cover your a**"

Certain manufacturers of critical components will go to the extent of specifying the amount of bolt elongation corresponding to the required bolt load. Thus, the mechanics in the field have a way of verifying the effects of the torquing process. If the specified torque target doesn't result in the required load, more force is applied until the necessary elongation is seen.