Quote:
Originally Posted by DuncanC
Bibio, Why would putting copper grease on the threads before tightening them up cause the threads to strip? Also stainless to stainless nut bolt combinations should never be done dry as there is a significant risk of the nut and bolt cold welding.
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copper grease is very slippy and putting the stuff on bolts before you tighten can strip the threads, especially if you torque to 'specified' or your ham fisted. SS bolts dont cold weld to SS nuts, problems arise when using aluminium in the mix as the two hate each other.
torque settings are for brand new threads mostly dry. applying a slippy substance to threads lessens the friction, less friction = less effort to reach a certain point.
if your going to copper grease any bolt threads and a torque wrench then drop the torque setting by 10-25% depending on how new each thread part is.
if you dont believe me there is a simple test. get some used and new nuts and bolts. clamp the head of a new bolt or nut and put in a vice, torque till the bolt or nut strips the threads or breaks then set the torque wrench at that torque. next apply copper grease to a new set of bolt/nut then repeat the process. repeat the above steps with the used nut and bolts.
now i'm not saying dont use copper grease on threads but be careful when you do and dont go mad with the stuff, a very very thin coating is all that is needed to stop corrosion. i like to dab around 1/8th of the thread tip in my copper grease tin then insert the bolt. only time i use copper grease is on external fasteners or blind holes that i know are going to cause problems later on like frame mounts etc.etc.
only time i use a torque wrench is on critical bolts inside an engine.
if your bolt has a 'shank' then you can put as much as you like on that part as long as its not touching the head or will squeeze out and touch the head which again will lessen the friction and reduce the torque.
applying copper grease or indeed any grease to external threads that have already been fastened up reduces the risk of them rotting and yes that includes SS. SS by itself wont corrode its other elements sitting on the surface that eat into the SS. Stain-Less Steel