On Nov 21, 9:11*pm, Eli the Bearded wrote:
Last week the garage door torsion spring snapped. It was at least
twenty-five years old and no one lamented it's short life. So a
day or two later we got the spring replaced, and a new garage
door opener for good measure. The door is wood, single car sized,
and quite heavy. I don't have any specs, but the spring is
clearly metal, so here I am.

I was not there when the installer was, but I was told he
recommended oiling the spring with WD-40 every three months. Now,
to me "oiling" and "WD-40" are not the same thing, but I can see
people confusing them.

I can see two theories behind why you'd want to oil the spring:
1) a light coat of thin oil will keep it from rusting; and
2) as the door opens and closes, the tension put on and released
from the spring causes it to rub against itself.

With the previous install, the rollers were occaionally -- perhaps
yearly -- lubricated with white lithium grease but that's it. At
the end of the life of the old spring, it had a small amount of
rust, but I don't think it caused the spring to fail early. Nor
did the spring look like it had worn down much, so I'm not sure
the rubbing action is very significant.

So what should I plan on doing?

Elijah
------
even if this isn't metalworking, it's metal

He wants to sell another job, so WD-40 is the recommendation. You
don't want rust, pits will start fatigue cracks in that highly
stressed spring. I don't think friction between the coils would cause
that much fretting wear. I would probably use LPS 3 for coating the
spring if I lived in a really humid area, a good grade of automotive
grease would probably work most any other place. Repeat if it shows
bare metal.

WD-40 probably wouldn't hurt that much but it's sure not either a
lubricant or a rust preventative. Maybe he's depending on the brown
crud buildup to shield things from moisture.

Stan