dan wrote:
RogerN wrote in

Metalworking, resizing copper tubing-

I measured the tubing and reads around .655", about .030" too big. I was
able to taper the end of the copper and hammer the compression nut onto
the tubing, this "sized" the tubing enough to get the compression sleeve
on and I got the valve on the line, but I would like to fix it better
later.

I could either shrink the tubing down to .625" or expand to solder a
correctly sized tubing inside the end of the old tubing.

Could you bore out one side of a coupling, and add a short length of
the proper sized tubing? Hmm, .030 is probably too much for a common
coupling to be bored out. Could you make a coupling(f/m adaptor?)
from a piece of brass?

I'd go with the turning, if OP has access to a lathe. Once, at the
shop where I sit, we needed some bizarre adapter for a vacuum pump,
and the boss said, "Hey, we're a machine shop. Just make one!"

It took about an hour, including learning how to turn a 1.25-32
thread!

But they also just happened to have had a perfect piece of brass just
lying there in the "cutoff" bin.

Cheers!
Rich