Hi Brian, here in the UK, snap head is the common term for a half
round rivet head. Simplest rivet head there is.
Oh. That's easy. (ish)
Step 1: how many do you need?
Step 2: do you have a fly press, or a kick press?
(yes, I know you have great bloody drop hammers, but this requires
something a bit less hungry for fingers.)
(And not nearly as much power.)
Depending on how many you've got to make, I'd make a steel block
that fit into the bottom die shoe of either a smallish fly press, or
a largish kick press.
Make one hole in the steel block just barely bigger than the OD of
your wire. (Maybe .20-.25mm bigger than wire. Tight enough the wire
can't crumple, but not so tight that it can upset to hole diameter
The depth of the hole depends on how many you need. If under 100,
I'd recommend snipping the wire and torch balling the end. If more
than 100, it gets a lot kinkier.
What I'd do if I had *lots* to do would be rig up a clamping system
inside the block such that you could feed raw wire up through the
bottom of the block, grab it, and then dome the head with the press,
but that's a lot of very serious machining. For 100-500, I'd snip
the wires all to a standard length, and drill the hole such that
about 1 diameter of wire stuck out proud of the surface. (If 1mm
dia. wire, leave 1mm sticking up above surface.)
Then rig up a steel block for the top die that just had a
hemispherical depression in it, of the diameter you need for your
Proceed to squish.
For the dead-end hole version, extraction will be fun. I suggest a
bench knife. I'd also drill the hole a smidge too shallow. start it
out with 2X OD sticking up. The wire will probably bend, but it
might not. You'll have to fuss with it to find the right ratio of
stick-up to head diameter, versus having the wire crumple.
If you've got a bunch to do, once you get the hole dialed in, drill
a bunch more holes and hemispheres, so that each press strike gets
you 6-8 rivets.
If it's just 100 or so, torch ball the end, and run the hole all the
way thru. Stick an air hose under the bottom and blow the formed
rivet back out.
You might have luck with a right angle hole intersecting the bottom
of the dead-ended hole for air blowout with that version. Just
don'tgive it anywhere where the silver can flow into the air line
and lock itself in place. (The more I think about doing the cross
drilling, the less it seems sensible. The silver will probably lock
into the other hole.)
You know, depending on how many you need, it may make more sense
just to buy them. At least here in the states, I'm sure I could dig
up a company that'd be willing to do a smallish (>1000) run of them
in sterling. Ask around in London or B'ham, and see if there are any
of the old manufacturers still around.
I know the folks at Sutton's in Birmingham, they seem like they have
a pretty good handle on the trade. They may be able to point you to
either someone who already has the tooling, or may just have a box
of the things sitting on a shelf somewhere. Ask for Geoff or Maggie.
Failing that, Mike at Walsh's down in Biggin Hill might know
someone. Can't hurt to ask. Some of the trade silver dealers might
know someone too. They have to get their silver somewhere..