Drilling out easy out

[B6T]

Originally Posted by JFP in PA

You would lose your wager. First of all, engines and transmissions are not assembled in the same plant the car is, they are shipped in from a facility the is setup specifically to assemble them, and they do use specialized lubricants on the fasteners. I've watched them do it.

Not entirely true. There have been plants that house both engine assembly and vehicle assembly under the same roof. Except in this context we're not talking about assembling engines, we're talking about some random M6 bolt that goes into a caliper. So my comment was regarding vehicle assembly, not engine assembly. Even still, only rotating assembly bolts are lubricated within an engine at assembly. Bolts that hold on accessories like the starter and alternator are not.

Originally Posted by JFP in PA

Secondly, the torque spec to reach the design clamping force is set with lubricated fasteners because dry fasteners will reach that torque spec level due to friction in the treads and at the bolt head before actually achieving the desired clamping load level, leaving the parts with less clamping load than expected.

You really ought to take the time to read the ARP paper, you might actually learn something.

I understand how bolting friction works, since that's exactly what I explained in my previous post, and what you explained as well. But if you're saying that a torque specification like those in a service manual require lubrication on thread to achieve that spec, I think that is where our opinions differ.

The designers for a vehicle understand what clamping force they are looking for, and to achieve that force they will specify a dry torque... which is much higher than a lubricated torque to overcome that friction, but still achieves the same clamping load in the end. I'm sure they do base it on a lubricated torque at some point, but the torque value you will see is for a dry fastener.

Why dry? Because when they're building the vehicle, lubrication on assembly lines is a) messy, b) an added expense, and c) from a torque calibration perspective, lubrication is an additional control point that can cause process variation since lubrication amounts, lubrication type, and even location on the fastener are hard to keep consistent. Way too many variables to control.

It is much easier to specify a dry fastener torque since the characteristics of a dry fastener are much much much more consistent and well established in proprietary design standards.