Two things occur to me: no professional jeweller would want to waste
time (it's money) when a similar mould can be bought.
Wanna bet? You can make a better one this way than the commercial
molds. The commercial molds don’t have the registration pins, and the
ingots almost always then have a nasty flange. Maybe not on the first
pour, when with cool molds you can carefully align edges, but the
second and subsequent ingots get poured into a mold a bit to hot to
comforably handle with your fingers. Those registration pins make it
a lot easier. Plus, the commercial wire molds like that are rather
short, if you want a longer ingot… Fine for the quantity of gold I
usually pour, but with silver? My home made mold lets me make a
serious amount of wire in one go. The time it’s saved in working
better has long ago repaid the few hours it took to make. One note.
I did the registration pins different, drilling a through hole right
through both plates. Then with a very slighly larger drill, I opened
up one hole a tad, enough so that the hole started as a tight jam fit
to the pin, and ended up on one plate as a smooth slip fit. Then the
pin was driven into the tight side. I feel this is quicker than
grinding a taper on the pins.
Incidentally, I use the same plates back to back with that bit
of tum square U shaped rod I mentioned in a previous note, clamped
between then to make a mould for a flat ingot.
Herbert Maryon describes much this same type of mold in his classic
book, metalwork and enameling (which should be in every jewelers
library. The dover reprint is cheap, and the info wonderful.) He has
one use a strip of sheet metal as wide as the desired thickness of
ingot, bent to a channel the width of the desired ingot, the open ends
flared a bit. Sandwich the both between smooth charcoal blocks and
hold with binding wire. You can make one of these in minutes, to give
you just the thickness and width of small custom ingot you might need.
Great when you need a rather small ingot for, say reusing some
customers gold, or a bit of some unusual alloy. And if you don’t
want to make it, Frei and Borel imports a nice little German ingot
mold that does much the same thing. side plates, a variety of inserts
with the channel, and a wire frame handle to hold em. Small, handy,
and not too costly.