I am getting some designs ready for mass-production, including some
earrings with posts. Is there any reason that it would be a bad idea
to have the posts integrated into the design before casting? Or is
there a better argument to soldering those posts on afterward for
some reason that is escaping me? (Laser welding will probably not be
an option as I am working on a shoestring).
Thanks!
Carolyn Tillie
Is there any reason that it would be a bad idea to have the posts integrated into the design before casting?
Carolyn, there are many reasons why the rule of thumb is “Don’t mold
findings”
They tend to be in odd places, so you get wierd molds. Take a
penny and mold it, and you’ll get a flat disk that will pop out of
the mold. Put on an earring post and you have a skinny wire
projecting a half inch down at a 90 deg. angle - an entirely
different mold.
It’s far easier to finish a piece and add the finding later, and
findings can and do get destroyed if they are cast in place. Take
that penny - you can prefinish the back nice and clean, because it’s
just a flat surface (we’ll say it’s a one-sided penny). Cast a post
and you have to finish all around a post in the middle - without
altering or destroying the post. The same if it’s a bale - you just
have a clean edge around the penny - if there’s a bale you have to
polish around it.
Shrinkage - your post will no longer be a post unless you size it
very carefully with shrinkage in mind - the clutch just won’t fit.
What goes hand in hand with that is the fact that any parting lines
on the post will make it garbage - that’s assuming that leaving the
lines is not an option, as is proper. And it will be rough unless
you polish it, which will also alter the dimensions…
Very often findings are better made with drawn metal, and cast
metal just isn’t right. I’d put earring posts in that category.
Generally, it’s penny wise and pound foolish… If you have
reason to do it, and it worrks for you, then fine - usually it’s a
bad idea. That doesn’t include things like pendants with a built-in
hanger that’s flush with the back and/or front - things that are
integral to the main piece. But the little bits and pieces like cuff
link backs always come out funky (and soft) and then the back is,
too, because the finding’s in the way…
Cast posts, if they actually cast successfully, would be entirely
too soft to function well.
Cast posts, if they actually cast successfully, would be entirely too soft to function well.
Sterling silver posts soldered onto earrings can get annealed,
therefore they can be soft. I used to do production casting and I
have mass produced thousands of cast 2mm-6mm round 4 prong cab
settings with the post attached. I have read where people suggest
twisting the post to work harden them, but when you are doing mass
quantities this is not practical. I do use commercial thicker style
earring posts on the pieces I mold so the posts don’t get too thin
from the shrinkage of molding, casting, and finishing. These parts
were tumble finished with stainless steel shot and I believe= they
were work hardened somewhat. I supplied these to several sources and
I had no problems with returns. I also used them for my store and I
did not have customers bringing them back for repair. My wife buys a
lot of sterling from overseas sources and we have more fabricated
jewelry returned for repair due to cold solder joints on rings,
earrings, pendants, bracelets than problems I had from the cast
pieces I made that we sold to our customers.
Richard Hart G.G.
Jewelers Gallery
Denver
The only finding I integrate into my castings is the pin joint. That
works very well. But I agree that posts are just too thin and fragile
to cast usefully.
Janet Kofoed
http://users.rcn.com/kkofoed
www.etsy.com/jkofoed