How to Turn 101 Copper?

[darkzero]

Milk sounds, um, icky? I've got mineral spirits, WD40, and oils of various viscosities.

WD40 will work. Last time I machined some copper (C110) I used Tap Magic Alumn. Glad I ran out of that stuff, I hate the smell, weird cause some people say it smells good.

Sulfur based oils can discolor or stain copper. You don't need a thick oil though, something low in viscosity will be fine, well that's what works for me anyways.

 

[mikey]

Nearly pure copper can grab, although it isn't that likely to happen when facing. I've turned a few copper bars that were C101 and its great unless it grabs and then it digs in. I used a HSS knife tool to face and it cut beautifully with stick wax of all things. I turned it with a brass turning tool - 15 degree relief angles and a flat top, honed well and a 1/32" nose radius.

Speeds are tricky. Its tempting to go fast but copper tends to catch and crack if something goes wrong. For such a large work piece, I would try facing it slow and see how it goes. Looking back at my notes, I turned my rod at 60 sfm and it worked okay with a slow feed. I suspect you can go much faster with a facing cut, though.

May I suggest you consider making a flange with an integral rod to fasten to the back of the piece. The shaft of the rod will go in the chuck and you can screw the work piece to the flange. If it catches, it won't go flying across the shop that way.

How are you going to finish it? If you want to preserve the copper finish, Everbrite might work but I'm not sure; I only used it on brass and it works well.

 

[darkzero]

What's the difference between C101 & C110? I've only worked with C110 round bar as that's what my local supplier sells. I used them for making heatsinks for the custom flashlights I used to build/mod.

Well I suppose I could just google it but I'm more curious about real world machiniability & application uses.

 

[mikey]

C101 is almost pure copper.

 

[tq60]

You may try visiting some electrical supply places and or contractors and ask for scraps of heavy copper solid wires or bolts.

Yes expect to pay for it but maybe scrap price.

Something to practice on.

Ask about returning chips or swapping your scraps if they just scrap it.

Scrap yard worth a look as well.

For tooling suggest trying a controlled cut form.

Meaning the edge needs to be very sharp but front relief small to limit the depth of cut.

The leading vertical edge near vertical.

It will drag so lube will be needed.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

 

[darkzero]

I see. According go wiki C101 is 99.99% pure & C110 is roughly 99.9% pure. C101 is oxygen free & costs more. C110 is electrolytic tough pitch, whatever that means, & is the most common grade.

Makes sense cause the metal supplier I go to is an industrial supply house, they mostly only stock common grades of metal in their retail & rem areas. Sucks cause the copper is only available in 6ft lengths min & you'll never find drops of copper, brass, or bronze in the rem area.

 

[brino]

I need a right cylinder ~7.875" OD and ~0.480" long. There is no ID. It's a disc.

Thanks for the clarification, I was picturing a solid cylindrical bar 7.875" long and 0.480" diameter!

When you said "taping" I thought you meant "tapping" it, since you went on to mention forming taps being available. Just goes to show how easy it is to mis-understand something.

-brino

 

[N2XD]

Basic difference is that c110 200-400 ppm oxygen and c-101 is certified low oxygen. I think its somewhere around 20 ppm. It's been awhile I might be a little off on the c-101 oxygen content.

 

[ACHiPo]

Nearly pure copper can grab, although it isn't that likely to happen when facing. I've turned a few copper bars that were C101 and its great unless it grabs and then it digs in. I used a HSS knife tool to face and it cut beautifully with stick wax of all things. I turned it with a brass turning tool - 15 degree relief angles and a flat top, honed well and a 1/32" nose radius.

Speeds are tricky. Its tempting to go fast but copper tends to catch and crack if something goes wrong. For such a large work piece, I would try facing it slow and see how it goes. Looking back at my notes, I turned my rod at 60 sfm and it worked okay with a slow feed. I suspect you can go much faster with a facing cut, though.

May I suggest you consider making a flange with an integral rod to fasten to the back of the piece. The shaft of the rod will go in the chuck and you can screw the work piece to the flange. If it catches, it won't go flying across the shop that way.

How are you going to finish it? If you want to preserve the copper finish, Everbrite might work but I'm not sure; I only used it on brass and it works well.

Mike,
As usual your comments are very valuable.

When you say "HSS knife", are you talking about a parting tool? How did you apply the wax?

I was thinking about bolting it to a faceplate (ala wood turning), but the flange idea should work, too.

As for finish, I thought I might just spray it with clear lacquer. Polyethylene glycol will form a thin passivation coating, but it is not very durable.

Evan

 

[mikey]

A knife tool is just a really good facing tool but a sharp general purpose tool will face just as well. The wax is just rubbed on the face with the part turning. I have heard of using the milk thing but I didn't like the idea so I tried stick wax and it worked well for me.

Look into Everbrite. I have brass and aluminum pieces that show no sign of corrosion or oxidation after being coated with this stuff. Better than green, I think.