I build myself a tool for expressly this purpose since, for a while,
it seemed that all that I was making were asymmetrical pendants. It
was a tumbled piece of Flourite shaped like Africa mounted on an oval
plate of pierced sterling that finally forced me to solve this
problem for once and for all.
So, what I bought was an old set of outside calipers at a flea
market. I paid pennies since they were slightly mangled but I knew
what I had in mind so the cosmetic damage didn’t much matter as long
as their basic mechanical function was intact. What I’m talking about
here is the ones used in lathe and woodworking, toolmaking or
drafting. The ones used in woodworking often they have flat legs. The
others are usually made from rounds stock.
What the tool is originally designed for is to measure the outside
diameter of a cylindrical object using a pincer type action. They
don’t actually have any measuring scales on them, they’re used for
transferring measurements from a model or drawing to a work piece.
They usually come in 4, 6, and 8 inch sizes. Smaller is better for our
purposes. If you can’t find an old pair like I did you can usually
pick up a cheapo pair for $6 or so from a discount hardware or lumber
supplies store. These will be totally satisfactory for our purposes.
I’m sure it’s obvious where I’m going with this: taper the points of
the calipers down, sharpen the points such as you might do with a
center punch and voila! a handy-dandy center-of-gravity tool that will
mark the suspension point when you gently squeeze the points into the
metal of your workpiece. The caliper’s span is more than enough for
the typical size of pieces we jewellery makers work with so you’ve
got plenty of latitude for shaping the points just how you like. With
these on the bench all the guess work about suspension points is