... They always come out too small and I end up having to spend an
extra 15 min. sanding out the hammer marks where I enlarged it.
I use a plastic or nylon mallet to do size-ups like this where you
don't want to mar the features of the ring. From my experience these
are better for this kind of thing than the traditional rawhide mallets
which I know some folks swear by.
Anneal and pickle the ring (if that is an option), slide the ring
onto a steel mandrel, position it so you're not hitting over the
numbers on the mandrel (don't want those numbers on the inside of the
ring) and have at it.
It takes a little longer this way because your mallet is
significantly gentler on the metal than a steel hammer is. Sometimes
you need to really whack it but it does work. A few trial runs and
you'll get the hang of it. Refinishing/polishing is almost never
necessary with this technique.
in The City of Light