Here we go again............
Brent, I know that you can't be wrong and you never are. But, with all do respect, you just are!
Finer threads have a larger CSA, just like a larger bolt has a larger CSA. There is no difference. It makes no difference what material the bolt is made of. It can be aluminum or 240K steel, the CSA never changes. A 1" aluminum bolt is weaker with a 8 pitch as opposed to a 1" bolt, with a 16 pitch and the 16 pitch. The 1x16 bolt will require a higher torque value, to attain 75% yield. Replace the word aluminum with 240k alloy steel and it will always be the same. The thread depth, is what makes the difference, alloys being the same. A 16 pitch thread has a depth of approx .0406 and a 8 pith, .0813. Therefore, it makes the root smaller along with the CSA.
As a graduate engineer, I'm surprised you would argue this point, it's simple mechanics. I'm posting a torque chart to demo what I'm talking about.
What I posted above, is the header to what you posted and the torque that ARP gives, is with engine oil. They don't recommend anything else.
Frank, I don't disagree with you on the materials engineering standpoint of it, but I will tell you that I will follow ARP's suggested torque specs for the fastener I'm using. I will also make adjustments based on my experience level with these engines and the parts that I use.
I will also make the following comments:
1. Torque specs vary depending on the material, fastener length, lubricant, thread design (rolled, etc.) and a myriad of other variables. ARP has different torque specs for each material.
2. I've never cycled any fastener 7 times, unless it's a fastener that's associated with a bearing clearance and I've had to loosen/tighten the fastener that many times in order to dial in clearances. As a matter of fact, your higher end rods, such as Carrillo, Oliver, Pankl, etc., will specifically specify to cycle the fasteners 2-3 times to burnish in the fastener's seating surface and then you're done. They will also specify which lubricant to use and I don't know of any quality rod manufacturer that specifies motor oil as a lubricant, because motor oil will not support the amount of pressure that's generated. ARP used to show torque specs for using their ARP lubricant and motor oil both, and the torque specs were greatly different. Now, with their most common fasteners, they will recommend ARP lube only, and when an ARP fastener (such as an L19, WS, etc.) is used on a high end rod where the torque spec on a 7/16" fastener will generate anywhere from 85-105 lb-ft of torque or up to .0065" of stretch, the rod manufacturer usually specifies something like a CMD high pressure lubricant.
3. Torque spec isn't the end-all-be-all of tightening a fastener. As Barry eluded to, it's the least accurate method of tightening a fastener. Torque/angle is very accurate but in the end, we're all trying to stretch the bolt to the correct length. On some fasteners, you can't check stretch, such as a head bolt, main bolt, head stud, main stud, etc. So, we rely on the bolt manufacturer's specs for tightening that fastener. In that instance, I'll pull out the piece of paper that comes with the fastener and use it.
4. When you have to use the torque (lb-ft) spec, you're more relying on faith that you got there, because you're trusting that the lubricant that's used is allowing the fastener to move freely, the fastener's seating surface is perfectly square, a washer isn't deforming, the finish is smooth, etc.
Only when you start using higher end tools, such as digital torque wrenches, stretch gauges, etc., that you can see what happens to a lb-ft torque value when you tighten a fastener. My digital torque wrench will measure lb-ft and degrees. When I torque a fastener using torque-angle, it will spit back at me what lb-ft we ended up at. I will tell you from experience that when the correct torque-angle is used and stretch is verified, the lb-ft value can vary by 5-6 lb-ft from fastener to fastener.
So, in regards to your bolt chart that you posted, that's all good for a Grade 2, Grade 5, or Grade 8 fastener, but it's not the end-all chart for those fasteners, because in all actuality (and I'll state again), torque specs vary with fastener length, the type of thread, the lubricant, etc. Above that, I will still use ARP's suggested torque spec for the fastener I'm using. Not only because I'm trusting that they have done their research, but my experience level gives me faith to do so.
I know you'll have some sort of retort that attempts to disqualify my engineering background, engine building procedures, or whatever, *but I simply don't care*, and I'm done discussing this with you.
