Bead Caps

[mizgeorge]

The doming actually takes so little away from the diameter that I would tend to stick with simple measurements, and look at the bead as a half sphere. So for an 8mm bead, I would generally go with a 4mm cap (8mm really isn't that big).

Most of the caps I make and sell are used on lampwork beads, and in general the 6mm size is good for beads up to about 15mm, and the 9mm size for focals (which are usually 18mm or larger in diameter).

I tend to keep the dome fairly shallow, and test the fit regularly - mine are often to make rondelle/doughnut shaped beads look just a little rounder, but I rarely need more than a dome that's equivalent to more than 1/4 of the diameter.

Hope that's not even more confusing!

[nickr]

I use 0.4-0.5mm sheet that has been annealed. I drill my holes whilst the discs are still flat and use a drop of paraffin as a coolant/lubricant which helps to stop burrs forming. I then shape them in a doming block. There is a formula for disc size to hemisphere size but cannot remember it offhand. Polishing in a shot polisher works but the half cups often sit inside one another so it can be frustrating. I either pattern the sheet when rolling to thickness or sometimes use the frosting wheels Cooksons sell on the finished article if I want a matt finish.
Nick R

[nickr]

I made a screw down punch many years ago, it looks like a bicycle chain rivet extractor.
Nick R