I’m developing some bangle bracelets for market that start out as a sheet of copper, which I cut into a blank shaped roughly like a 45 rpm record. Sawing works, and it doesn’t take too long, but it’s not my favorite part of the process.
I’m not real excited about having dies made at this point – let’s see if the market supports the expense first!
Here’s my idea: attach the sheet to the faceplate of my wood lathe and use a scribe of some sort to cut the circles out. Does anyone have any better ideas?
sure, work at low rpms, use a carbide lathe cutting point in a tool holder, and that should work. beware machining copper it is soft, likes to grab the tool and the workpiece can go flying.
Sizes will be between 2.75" and 3.75", more or less to accomplish various sizes, with a hole in the middle between 1.5" and 2", more or less.
I don’t have a hydraulic press (yet!). That would be the best way to go, but I want to test the market for my bracelets before plunking down that kind of cash.
I’ve made a thing – don’t know what to call it – to mount on my faceplate. It’s all faced off nice and flat, and has a 4" square depression to mount my blanks in. I’m hoping the lip around the blank will help ward off any “James Bond/Oddjob” episodes, as I saw someone else describe it over on a woodworking site. Don’t want to get blood on the floor if I can help it!
I figured I’d need carbide to cut with. I’ve spotted a $16 paint scraper with a three-cornered carbide insert that looks like it will do the trick. There’s also the $60 actual turning tool at Woodcraft. I’m guessing copper won’t ruin the tool, so probably springing for the real deal is the way to go. Off to Woodcraft tomorrow.
I really hope this works. The bracelets are coming out really nice – hoping I can work the process out so I can sell them at a price the market will bear. Wish me luck.
For turning copper you’re better off with HSS tools than carbide. You will need to find a metal lathe tool holder that will fit the ways of your wood lathe. You should pick up a book on running a metal lathe, and you’ll need to learn to sharpen your tools when they dull, though turning copper will not dull them quickly if you keep the tool cool while turning. You need cutting oil to lubricate the cut and keep the tool face cool.
A metal lathe manual or guide will also give you the best angles to grind on your tools for turning copper. You’ll probably want to use a parting tool to cut the circumferences of your disks.
The kind of chuck you describe is called a jam chuck. Usually these have a concave cone and are used for holding spherical objects.
However, since you’ll be cutting a hole in the disk you can secure it to your chuck with a nut and bolt through the center of the square blank, this will keep it inside the depression and the square depression will help keep the blank from spinning on the axle created by the nut and bolt. This way you should be able to part off the larger diameter of the disc from the square and then part off the central hole in the large disk.
It might be useful to join an online metal lathe forum and ask advice there.
I would use HSS on my lathe to cut copper. I would probably gang 4 or 5 disks together sandwiched between large washers just under the diameter size bolted together. You could even use wood washers. Copper is just so soft to cut on a lathe. I would sure try to find punched disks. Even on eBay
My first attempt didn’t go very well. I was using carbide, not HSS; I forgot to use oil; and I was trying to just hold the tool still – wood-turning style – instead of mounting it, metal-machining style. I’ve investigated tons of other ideas, and nothing else is coming close to panning out. I’ll try fixing the three issues listed above, and see what happens. I’ll also try fixing up a better jam chuck. The first go isn’t as nice as I’d like.
I sometimes wish I had the capacity to give up on an idea, but no. I just can’t let it go until I’ve proved it either can or can’t be done.
Are you attaching the disks to the chuck with a through bolt, as I suggested, or just relying on pressure from the tailstock ram? If the latter, you may not have enough contact between the tailstock ram and the disk. You should do a search on youtube for metal spinning. That’s a trade which mounts disks between the headstock and tailstock using only pressure from the tailstock ram.
