Short answer is yes, he's correct, Jerry.  But the stuff sold in coils
is already annealed to allow for a certain amount of forming.
Shouldn't be an issue unless you need to make a pretty sharp bend or
two.  Otherwise, keep the radius of your bends as large as possible
and put in a bit of effort to get it right the first time to minimize
reworking.  Err to the side of not bending your angles far enough the
first time to avoid working the bends back and forth.    Years ago, I
watched a friend, mechanical engineer, put a fairly tight bend in a
piece of tubing.  He had access to liquid nitrogen, so he filled the
pipe with water & plunged it into a bucket of the stuff to freeze the
water and bent the tubing around a pipe of appropriate diameter.  I
suppose you could do the same if you can get the filled piece into
your home freezer.  As far as further annealing goes if you find it
necessary, heating to a red glow is getting very close to the melting
point for copper and might be difficult to do successfully absent a
tightly controlled environment.  But it's probably not necessary to go
that far.  I recently annealed a copper disk enough to allow some
clean forming by heating just to the point it turned a dull blue and
letting it air cool.  I'm not at all sure that annealing relieves work
induced stresses though, so if you're needing to do some real
aggressive bending, you might want to read up on that a bit.

HTH,

Joe

On Apr 6, 2005 10:28 PM, Gerald Masar <azsun99@earthlink.net> wrote:
> I am finally finishing a too long project to add a second propane tank to my '90
> Westy, and have a question for the metallurgists (or anyone who knows) on the list.
> Yesterday I bought some 3/8" O.D. copper tubing to connect the two tanks, and while
> the clerk was coiling it up very carefully, he said you don't want to work it too much
> because it causes it to harden. He called it "work hardening". True or false??