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How to Turn 101 Copper?

ACHiPo

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#1
I just ordered an 8" x 1/2" slug of forged 101 copper. I want to turn it down to a 7.875" x 0.480" cylinder.

I've heard horror stories about how hard (soft) copper is to machine. This is largely a decorative piece, so dimensions aren't critical, but I'd like a decent finish on it.

First question--how do I chuck it? I've got a Logan 816 (10" swing) with 3-jaw and 4-jaw chucks, but I'm thinking taping it or screwing it to a faceplate would be my best bet? I do have forming taps so can screw into the copper from the back.

Next question--what tool should I use to face it and turn down the diameter?

Last question (for now)--what speed and feed?
 

aliva

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#2
I've turned some copper, the problem being its very soft. I tried carbide CCMT inserts with a so so result. I then tried HSS with a very small nose radius and,sharp , results were very good, so I would recommend HSS. Don't take too big of a cut as the copper will heat up and may want to fold over at the cut line and pieces will stick. Keep the feed rate between 5 and 8 thou/rev The speed should be 300 to 600 rpm. Pick which very gives you the finish your looking for, you can alway clean things up with emery and scotch bright. As far as chucking, go with the 3 jaw if you can afford to loose a little length in the chuck. Try and keep the stick out to minimum. If you need the entire length turn between centers using a lathe dog. Hope this helps.
 

ACHiPo

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#3
Thanks. Definitely gives me a starting point.
 

darkzero

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#5
For carbide, I use CCGT alumn specific inserts to turn copper. These inserts have a high positive geometry & are very sharp. Any other common molded insert won't leave a good finish. And use lube as the copper tends to smear. But HSS would be a better choice, key is to have a very sharp edge for a good surface finish.
 

Wreck™Wreck

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#6
I just ordered an 8" x 1/2" slug of forged 101 copper. I want to turn it down to a 7.875" x 0.480" cylinder.

I've heard horror stories about how hard (soft) copper is to machine. This is largely a decorative piece, so dimensions aren't critical, but I'd like a decent finish on it.

First question--how do I chuck it? I've got a Logan 816 (10" swing) with 3-jaw and 4-jaw chucks, but I'm thinking taping it or screwing it to a faceplate would be my best bet? I do have forming taps so can screw into the copper from the back.

Next question--what tool should I use to face it and turn down the diameter?

Last question (for now)--what speed and feed?
Do you require a 7.875" OD X .480 ID "cylinder of unknown length?
Or a 7.875" OD cylinder .480" long of unknown ID?
 

kwoodhands

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#7
I just ordered an 8" x 1/2" slug of forged 101 copper. I want to turn it down to a 7.875" x 0.480" cylinder.

I've heard horror stories about how hard (soft) copper is to machine. This is largely a decorative piece, so dimensions aren't critical, but I'd like a decent finish on it.

First question--how do I chuck it? I've got a Logan 816 (10" swing) with 3-jaw and 4-jaw chucks, but I'm thinking taping it or screwing it to a faceplate would be my best bet? I do have forming taps so can screw into the copper from the back.

Next question--what tool should I use to face it and turn down the diameter?

Last question (for now)--what speed and feed?
I have seen turpentine or milk used as a lubricant. One of my cousins is a machinist and he uses turpentine, HSS and compressed air to cool the work while turning. I have only turned and faced copper twice, both miserable experiences.
 

ACHiPo

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#8
For carbide, I use CCGT alumn specific inserts to turn copper. These inserts have a high positive geometry & are very sharp. Any other common molded insert won't leave a good finish. And use lube as the copper tends to smear. But HSS would be a better choice, key is to have a very sharp edge for a good surface finish.
I think I have some CCGT inserts. I also have a bunch of HSS tools which I can learn/practice sharpening. Given that the slug is over $100, I may try to find some smaller pieces to practice on first.
 

ACHiPo

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#9
Do you require a 7.875" OD X .480 ID "cylinder of unknown length?
Or a 7.875" OD cylinder .480" long of unknown ID?
I need a right cylinder ~7.875" OD and ~0.480" long. There is no ID. It's a disc.
 

ACHiPo

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#10
I have seen turpentine or milk used as a lubricant. One of my cousins is a machinist and he uses turpentine, HSS and compressed air to cool the work while turning. I have only turned and faced copper twice, both miserable experiences.
Milk sounds, um, icky? I've got mineral spirits, WD40, and oils of various viscosities.
 

darkzero

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#11
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

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#12
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

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#13
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.
 

tq60

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#15
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

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#16
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

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#17
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

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#18
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

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#19
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

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#20
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.
 

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#21
One question I have; How hard is the copper? Is it 1/8, 1/4, 1/2 or full hard?
 

mikey

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#22
One question I have; How hard is the copper? Is it 1/8, 1/4, 1/2 or full hard?
Dunno how to answer this one. The only copper I have turned is the C101 stuff and it is supplied as a nearly pure copper bar that was extruded. Copper is one of the softest metals in common use so its pretty soft.
 

Wreck™Wreck

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#23
As far as turning there are inserts made specifically for copper , if you have many parts to make this would be the way to go.

When only a handful of parts are required I have had excellent performance with aluminum specific inserts turning large copper electrical conductors. I would not do so without flood coolant however.

If only making one part go slow and use sharp positive rake tooling, the finish doesn't appear to improve with speed in this material, for drilling and tapping lard oil works a charm but is nasty in many ways.
For holding I would pocket soft jaws 1/8' deep and face one side then turn as much of the OD as possible, flip then face to length and turn the rest of the OD as needed.

Like so, one face and most of the OD finished, then flipped and faced to length and the rest of the OD turned. 42 parts in 304 SS, the order was for 40 but I made 2 extra because they get a good deal of mill work done to them afterwards including some 4-40 tapped holes, if a tap is broken in one I would have to set up the lathe again to make 1 more so I planned ahead.
 

Rustrp

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#24
Dunno how to answer this one. The only copper I have turned is the C101 stuff and it is supplied as a nearly pure copper bar that was extruded. Copper is one of the softest metals in common use so its pretty soft.
Since my work has been in sheet and bar stock I wasn't sure how the temper would affect turning or other machine work. I know drilling (I use 118°) and tapping is all about sharp tools and lubricant. In regards to hardness, my experience is working copper is the reverse of steel and I guess the easiest example to explain would be when I tin my soldering irons. If I heat them up and allow them to cool they are harder than when dipping them in the sal ammoniac water solution to keep a good tin. The hardness I mentioned is achieved through cold working or pressure applied during the rolling/drawing process. I usually use 1/4 -1/2 hard for most products.
 
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