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Machining sterling silver

#1

Hello all,

This is a different approach, but I am adapting yet another series
of techniques, so here we go.

I have cast some large cups, both in sterling and fine silver.
(total cast was about 800 grams, trimmed down to about 575 grams
after sprue and gate removal).

Now, one of the steps I am doing is machining these on a sherline
lathe - lets me superimpose a perfect machine circle on top of a
hammer finish, for contrast.

Anyone in the group have experience machining sterling, I am having
some trouble with “galling” when cutting.

Mark Zirinsky, Denver
"private cutter buying rough and collections"

#2 
Anyone in the group have experience machining sterling, I am
having some trouble with "galling" when cutting.

Hi Mark,

I’m not sure what you mean by “galling” but my experience machining
silver is that it can be what I call “sticky” - the finish is rough.
My instructor, a one-off watch maker, suggested dulling the tool tip
slightly with an arkansas stone or similair fine-grit stone when we
were machining silver. We ground our own tools from tool steel -
sometimes it takes some fiddling before you get the right angle on
your tool bit - in combination with lathe speed.

Sorry I can’t be more specific - maybe someone else has more
specific advice.

Cheers,
Donna Hiebert

#3

Hi Mark,

Anyone in the group have experience machining sterling, I am
having some trouble with "galling" when cutting.

I’ve never tried turning silver, but have run quite a bit through a
mill. Milling it presented no problems.

A little experimentation with height of the cutting tool & tool
geometry may help. You might also try a light coat of lubricant on
the piece being turned. If you don’t have any of the commercially
available ‘cutting’ oils, try liquid dishwashing detergent just as
it comes from the bottle.

Dave

#4

Mark,

We machine a lot of sterling and we use lab grown diamond tooling
which gives an unbelievable finish, almost polished If you are
willing to outlay the money that’s the way to go. It’s pricey but
with proper care it will last a long long time. You can also have
it resharpened when it does get dull. AIt also helps to use lots of
coolant to keep the silver cool. As you know it heats up rapidly.

Tino Volpe Metallurgist,
Technical Manager
Tiffany & Co.
300 Maple Ridge Drive Cumberland,
RI 02864-8707 401-288-0124
@Volpe_Constantino

#5

Mark,

Before I offer an explanation, I need to know what your chips look
like. Are they long and straight?, Are they Long and Snarled?, Are
they long and in a helix?, are they full turn Chips? meaning that
they are short and have curled to almost a closed loop?, or Half
Turns which would be a short Chip with a half Diameter/Radius curve
to them? or are they tight and look like they were jammed at one
point?.

Also, I need to know your tooling set?

Are the tools Positive or Negative Rakes?. Do your tools have a side
rake?, what is your shear angle on the tool and lastly are you
running them as a point or does the tip have a Radius?

Best Regards.
Neil George
954-572-5829