View Full Version : Precious Metal 2 Start ACME

07-02-2007, 08:55 PM
This is probably confusing. But I have this project where I neeed to create a bracelet using silver or gold wire that resembles a 2-start ACME screw. Most likely it will be a maximum of 3/16 inch major diameter. I've looked at all the available profiles and can't find anything that looks like this.

Anyone have any ideas? Thanks, Paul:confused:

07-04-2007, 10:26 AM
I'm a little unsure of what you're trying to make.

If you're looking for a gold or silver wire with an acme profile, forget it.

If you're trying to wrap wire to make an acme profile, doable but difficult.

You could mill or turn a replica of a acme screw in wax, have it cast and bend it make a bracelet. Or, make a mold off a piece of acme, cast a wax and then cast that in gold or sterling.

Add balls or other decorative ends to it, it'd look nice.

07-04-2007, 11:55 AM
Yeah, just wanted some confirmation that somewhere in the world there wasn't some wire profile that looked like an ACME or Trapezodial 2 start screw.

I was considering casting from a wax pattern. Where I was in a quandry was; shape before casting or attempt to take a cast piece and shape it into a bracelet. I've never tried to shape a casting, so I'm not sure how doable that is before it fractures.

I was actually looking for some small acme screw (3/16 or less major diameter), which I was going to anneal, cut and shape and then have a mold made from that.

The bracelet will have a secondary operation, adding a couple of pairs of twisted wire (right and left hand twists) in one of the starts (end to end).

Thank you for the information.


07-04-2007, 12:26 PM
I've never seen a wire like that, although a wire would work better for a bracelet of that diameter. People like to fiddle with their jewelry, so if they are bending a bracelet back and forth, a casting is going to crack way before a wire. A wire would be the way to go if you were making these as production pieces. A bigger, stronger bracelet wouldn't bend, so that's another option as well, especially for silver.

You could try making a draw plate with the profile, or actually a sucession of profiles, starting with round, and produce your own wire, then twist. You could create a wire with the right profile pretty easily but I don't know if you could get enough twist without deforming it, to make it look right.

Could you just roll threads in? Gold and silver are pretty darn soft.

Gold and silver are more malleable than steel when cold, so if you're going to cast then bend, you can anneal the gold/silver then bend. If it starts to stiffen up/work harden, re-anneal. As long as you have a good, solid casting it'll work. Annealing the steel rod and making a mold would work as well.

You can use a baseball bat or something similar as a mandrel to shape the bracelet with a plastic or rawhide mallet. Start in the middle and work towards the ends. It's helpful to have a template drawn on a piece of paper to lay it on as you work, to get the shape right.

I would suggest a couple of things for mold making and casting depending on your design. If it's acceptable, smooth the inside of the bracelet, it might make it feel better on the skin, but mainly you could have a mold line just on that inside area, it'll make it easier to clean up. Getting a mold to line up and cleaning up the mold line in threads is a PITA. You'll also have to plan on smooth areas to sprue to, either the ends or the inside.

08-21-2007, 11:00 AM
I'd just create a cross-section and wrap it in a helical fashion around a centroid in RhinoCAD.