Quote:
Originally Posted by B6T
Standard practice, at least in automotive assembly, is NOT to lubricate threads and or washers. In specific applications, lubricant may be called out, but those are the anomaly. ARP might claim to lubricant "ALL" threads because in their world of specialty high strength fasteners, this is the standard they can expect from the users of the product since they have a specific attention to that detail. But I'd wager that you wouldn't find a single lubricant near any fastener in an automotive assembly plant.
A specified level of torque applied to a fastener head will result in more clamping force when the fastener is lubricated than when it is not lubricated. The reason is because you are reducing the friction between the thread flanks and thereby increasing the tension in the bolt. Hence, if you lubricate the threads and apply the specified torque value, you run the risk of breaking the bolt or the mating parts since you are applying a greater clamping load than intended. Bolted connection design takes into account all these factors and the design engineers follow proprietary tables when they size a bolt for an application, which for the most part, is a dry fastener that has a reducing clamping load than the same fastener when lubricated.
VW/Audi/Porsche flywheel bolts have a thread locking compound that will not work properly if you lubricate the threads with oil.
I don't know what the hell ARP is talking about, and I don't have time to read it, because I own a Boxster which is waiting for me in the garage.
|
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. 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.
Threaded Mode
