There is a commercially made coupling that fits inside of 1/2" copper tube.
You will not find it at most big box stores, probably at a plumbing supply
house, they are hard to find.
I had used one in the past but cannot remember where I got it.

You may be able to locate some 1/2" outside diameter copper tube that will
just fit inside a 1/2 inside diameter copper plumbing pipe. A little
soldering and you are back in business without tearing apart any walls.

"Noozer" wrote in message
news:bT_1i.183436$6m4.123878@pd7urf1no...

"vic" wrote in message
ups.com...
I replaced a bath tub spout with a Danco spout made to replace the old
Moen spout.

I made a big mistake by cutting the 1/2" copper nub coming out of the
wall to less than the minimum called for. The minimum length of the
copper tube distance from the wall was 1.5", I cut it to 1". This
resulted in water coming out of the back of the spout when I use the
shower diverter on the spout.

Am I missing another option that would be simpler?? (NOTE I can't
solder a coupling and a copper tube section to extend the copper tube
from the wall as the coupling would interfere with the spout
installation, not making it flush to the tile)
Thanks for your help!

I may be way out in left field here, but is there a butt joint for copper
that will fit INSIDE the pipe?