Oiling of threads when torquing down

Question

Oiling of threads when torquing down

fx57 (Mechanical)

(OP)

11 Dec 01 03:51

I've just entered the world of american motorcycles where they recommend putting oil on the thread of a stud when torquing the nut down to reduce friction and give a more accurate torque reading.
I have had japanese motorcyles for 20 years now and never come across this.
Is oil the right way or wrong way? I do not want to reduce friction to far and cause failure. I was told this is why you cannot use moly on threads as you will wind the thread off?
Please educate me.
thanks

TheBlacksmith (Mechanical) · Answer 1 · 2001-12-11 08:54:08

Follow the shop manual. When you torque a bolt, you are actually clamping the head to the engine, etc. On big industrial equipment, where the bolts are 1 1/2 - 2 inches in diameter (or more) many times you will measure the bolt elongation. This is not practical on small bolts, so the engineer figures out how much resistance to turning (torque) will occur at the desired bolt elongation. Since the torque you see is both the bolt stretch and friction, it is important to follow the shop manual. Some say "clean and dry"; some say dipped in motor oil; some say "coat with anti-seize". These are not arbitrary, the engineer figured that lubricants properties into his torque recommendation. Following the right procedure should not result in the bolt coming loose.

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Oiling of threads when torquing down