I'm no metallurgist, but I did some reading and found that the important specification would be the tensile yield strength. For 6061 Aluminum, there are a bunch of different numbers, but most agree somewhere between 240MPa and 290MPa.
I just don't know how to translate that into useful information. I can probably calculate the rotational force of 8Nm exerted on a 6mm bolt with 1mm pitch threads and come up with a linear pull force, but I don't know how to compare that to the material spec.
Maybe we have someone on here that knows that side.
Forget whatever you learned about Archimedes. The clamping force you'd expect due to geometry isn't achieved because friction dominates. Find tables of clamping force vs. torque for thread materials and sizes, dry or wet. Or, coefficients of friction. The clamping force is what shears threads (so deep female threads in aluminum can be a good match to steel bolts, which don't stretch enough to strip threads like a zipper, instead spread force over entire depth.) And then the clamping or rotational force shears the inner diameter of the bolt thread.
I did go through that exercise to determine if some over-torqued aerospace components had been stressed beyond limits (potentially starting to shear the threads.) In that case they hadn't. Although I'm primarily an EE, my assignments have had me venture into other disciplines.
I once selected tiny stainless bolts to clamp an aluminum heatsink and broke them, before realizing they had half the strength of carbon steel.
I think aluminum bolts/studs for the battery will allow far less clamping force than stainless would, but it's possible they can tolerate the maximum torque specified.
When you torque terminal bolts, it is possible the plastic is limiting factor, not the aluminum. In that case, if you restrained a stud (e.g. with allen wrench or wrench on a pair of nuts), I think you could engineer a higher torque and clamping force based on aluminum thread strength and stud strength, without regards to battery manufacturer recommendations.
And by the way ... we are taught that a cheater handle only reduces the force needed to turn a bolt, does not reduce the torque.
That is incorrect.
Radial loading increases the friction which resists turning a bolt. Longer cheater handle, less radial load for a given torque, more likely you can get the bolt free without applying too much torque and twisting it in half.
Torquing a battery terminal, longer handled torque wrench means same torque achieves more rotation of bolt thread, more clamping force.
Same effect can be achieved with a T handle wrench (perfectly balanced force, none taken by bolt.)
Or just use an extension between torque wrench and socket. You use your palm to restrain head of the wrench from flopping; no radial load on bolt, all torque goes to overcoming friction due to thread ramp and to providing clamping force. No extra friction due to radial load.
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