How do you get this shape?

I occasionally use stamped or pre-formed pieces from Stuller, Rio,
or Metalliferous when they provide a shape I can’t get (or can’t
figure out how to get) any other way.

One of my favorite shapes is a scallop shell, like the famous “venus
on the half-shell” Botticelli painting (yes, I know that’s not the
REAL title, but everyone will immediately know the one I’m talking
about). It’s basically a circle that has been corrugated “top to
bottom” and then made concave. At the top of the shell, the
corrugation is much closer together than at the bottom, and the
corrugation ridges are usually quite small. I’ve used these pieces
up to about 1.25" in diameter. You can see a picture online at
www.stuller.com http://www.stuller.com/ , product # 3886. (This
isn’t exactly it, as this one has a flat area at the base of the
piece and the ones I use have corrugation extending all the way to
the edge.but it’s close.)

However, I’ve never succeeded in replicating them. When I corrugate
using the bonny doon brake or the industrial tube wringer, the
corrugation is MUCH bigger than on these pieces. And even if I
crimp along one end, it still doesn’t give the same effect. Doming
the piece then “flattens out” the corrugation.

SO. have any of you made these pieces and, if so, what set of
techniques did you use? I’d love to make them in a variety of sizes,
as well as some variations, since I like the design.

@Karen_Goeller
Hand-crafted artisan jewelry
http://www.nolimitations.com

    I occasionally use stamped or pre-formed pieces from Stuller,
Rio, or Metalliferous when they provide a shape I can't get (or
can't figure out how to get) any other way. 

It looks like it’s made from a two-part repoussee die. These forms
can be made from the dies by hand or by press. If by press, anything
heavier than 24 ga. will have to have at least a 50 ton. The two-part
die consists of a punch and a die, one positive and the other
negative, in order to form the crenallates that will hold their shape
without losing form with further shaping. Tucker Tool Co. out of
Arizona sells pre-made two-part repoussee dies. However, expect to
pay around $125 for the die, plus additional $$$ to have it fitted
for press work. You will also have to true the die, register and dress it
before it can be used.

You can make your own two part mold for the hydraulic press with
this really hard mix and pour stuff you put into a frame. Check the
boonydoon.com site and Susan Kingsley’s book on die forming.

Elaine Luther
Chicago area, Illinois, USA
Metalsmith, Certified PMC Instructor
Studio 925; established 1992
@E_Luther

Karen,

If you have a Bonny Doon press, then you can make an acrylic or
Delrin or metal or epoxy die.

In “Hydraulic Die Forming for Jewelers and Metalsmiths”, Susan
Kingsley advocates making a conforming die from pourable
steel-filled epoxy. She actually shows and example in the book of a
shell form (not the exact shape that you are referring to, but close
enough for you to get the idea).

It’s a really good book for
–Terri