I have a little experience turning sterling. I do it using a Jacobs
chuck to hold the workpiece. I cut using either a graver or a
pyramid tipped tool, manipulated by hand rather than a cross slide.
I should mention that the graver here is a turner’s tool rather than
an engraver’s, is bigger and not tempered as hard.
The silver cuts very much like copper or aluminium. The description
that comes to mind is sticky. If the tool catches the workpiece the
workpiece is likely to be damaged as it is soft and easily
distorted.
There are things I do that may help. The silver is wrapped in
masking tape where the chuck holds it to protect the surface.
The lathe runs at about 2000 rpm for a workpiece about 6mm in
diameter. The cut is very light, the shavings like cobwebs. Because
the tool does not penetrate much its exact shape is not very
important but it ought to be sharp.
I use a cutting fluid. Cooling is not an issue but swarf building up
on the tool certainly is. The surface quality is much improved and
the chance of a catch reduced. I usually use saliva but I am sure
any tapping fluid or burr lubricant would do. If I planned to
machine silver for hours I would buy cutting fluid from an engineers
supply shop. Something designed for aluminium would be a good
choice.
Chris