Hi Vic,

Obtain some larger and longer section copper, then anneal, then roll in rollers. Most ME clubs have a large set of rollers.

You might need a few anneals and passes on the rollers. Silver solder the joint with high melting point silverflo 24 and Thessco F or Tenacity 4 after trimming the ends. Then maching to final size.

Or else get a slab of copper and machine the ring out of it. Ok very expensive but I know of many model engineers who have thick slabs of copper ( My 5"g terrier copper cap for the chimney was done this was by the very generous help of one model engineer providing an offcut of 3/4" copper slab).

What ever you do get it passed first by your club boiler inspector.

Cheers,

Julian

You could do it in a press or even heavy bench vice using 3 pressure points and working along the length, best done as two half circles as 6" is a bit small and will close up around the press/vice.

This is the sort of thing

Quite controlable once you get the feel for it

Another option may be to make it out of a couple of rings cut oversize from 4 or 6mm material lightly rivited and then soldered into one piece with a high temp silver solder. Then turn to fit your tube and solder with a lower temp one.