In a message dated 5/15/02 8:42:25 AM Eastern Daylight Time,
PilotRob@webtv.net writes:
> What would you recommend to prevent
> rust, etc. and/or how should the torque
> value change? Too what extent...by how
> much?
>
I like that copper based anti-seize stuff. And I am not an engineer, but
here is a quote from the Bowman Technical Series "Fastener Facts" book:
"The effect of lubrication is obvious through the fact that the recommended
"dry" assembly torque for a 1" UNF Bowmalloy cap screw and Bowmalloy nut is
1250 ft-lbs. When the same bolt and nut are lubricated with Bowman
anti-seize compound, it requires a torque reduction of 40%. The recommended
assembly torque is now only 750 ft-lbs., which will produce the SAME amount
of clamping force as the dry torque."
"Suppose a mechanic is working on a fairly dirty repair job and walks over to
the bolt bin to obtain some replacement fasteners. As soon as he picks up
the bolt and touches the threads with his greasy fingers, he may as well
throw the torque wrench and torque chart out the window. He just lubricated
the bolt with oil from his fingers!"
"Because of the dangers of accidental lubrication the Bowman Distribution
Engineering Department strongly recommends that ALL fasteners be
intentionally lubricated with a known lubricant, using lower torque values.
Lubrication reduces the amount of torsional force to the fastener,
tremendously decreasing the chance of installation failure while increasing
the longevity of the bolted assembly."
On page 83 of the book is a chart that shows towque values for different
grades and sizes of bolts with the values for dry threads and for lubricated
threads. For instance, a SAE Grade 5 7/16" Fine thread bolt shows a torque
value of 49 ft-lbs. for dry threads and 30 ft-lbs. for lubricated threads.
--David C.
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/spridgets
|