Have you ever needed to machine copper

I would hang on to it. I have the occasional need to make bus-bar "bugs", and other high-current connectors and contacts.

Last year, I had to make all new rheostat studs for my very (very) old EZ-GO golf cart. They'd discontinued the part.

Nothin' for it but copper rod, lathe time, and some frustration getting my rake angles right.

(single-point threading of copper is a pain in the ass!)

LLoyd

That stuff that you made, you could not make out of 1/4" copper bar, is that true?

I did find several occasions where a big 1/4" thick copper bar was useful, indeed.

I think that I will agree with you and hang on to this bar.

i

One suggestion: don't anneal it until after you machine it, whatever you do. You will pay for it in utter misery.

I was involved in machining 2000 cylindrical electrical connectors, 1-1/4" diameter and 3" long, once upon a time. The harder the copper is, the better.

-- Ed Huntress

The rheostat studs were made from 3/4 round. But I've made bus-bar connector blocks as large as 2x2x2.

LLoyd

I'll remember that. Maybe even harden a piece before I work it. In this case, it was "run whut you brung". I got a stick of whatever the metal shop had, and didn't think to harden it before working it.

"Razor-sharp chewing gum" comes to mind.

LLoyd

OK. Thanks. I will definitely hang on to it.

i

What's wrong with you? I am unable to conceive of why anyone in their right mind would even consider letting a piece of ANY metal larger than a cubic inch, out of their clutches. Excuse me, have to go, just heard a bunch of noise from the garage, where I think a shelf collapsed....

/mark

Ignoramus5693 wrote:

I am looking for steel and aluminum pieces, actually. I had doubts whether I need a copper bar of that size (I have other copper bars that I actually used).

The real problems begin when there is so much stuff in the garage that it turns into a Black Hole.

i

The easiest way to find that out is to sell it.

Nick

Copper is the nastiest stuff I have ever machined. Being a good heat conductor, soft, sticky, etc, it's just aweful. I made a number of custom cable swages for 1/8" aircraft cable, and it was a nightmare.

8 feet of 1/4" dia copper round bar got turned into 2" long pieces, faced both ends, and drilled through with a #29 drill. Some got stuck in collet blocks, clampled a wierd angles, and fishmouthed in preparation for brazing, while others got threaded #10-24. In the process I snapped 4 #29 drill bits and had my lathe drill chuck (this is a large toolroom lathe with a lever collet closer) pulled bodily out of the tailstock by the stickyness of the copper. It also transmitted heat very effectively, to the point where the heat of the drilling operation (this is with extensive mist coolant, no flood available) heated the collet to the point where it expanded and did not grip the part firmly. The project turned out well, but it was one of my least favorite machining experieces.

(I think I screwed up the original reply and sent it just to Lloyd. Hey, I'm rusty...)

Sharp chewing gum it is.

However, I don't know how you'd harden the copper, unless it was some alloy that can be heat treated or whatever. Pure copper, and most alloys, can only be work-hardened. Their hardest state usually is the condition they come in, right from the mill. The trick is to leave them in that state.

-- Ed Huntress

One thing a big solid chunk of copper is good for is balling tungstens for use in welding aluminum. In fact, I would love to have a chunk of that bar two inches long if you ever decide to saw it up.

An old machinist once told me that if you do have to machine copper the cutting fluid you want to us - really, this isn't a gag - is milk! I think he suggested a can of evaporated milk.

Grant

"Ed Huntress" wrote in news:WL0si.11$ snipped-for-privacy@newsfe12.lga:

It machines really nice with PCD tooling. I used to size printing cylinders right out of the copper plating bath, prior to engraving and chrome plating. The biggest issue was birds nests.

Yes, that's a problem, especially in production. I reported on an operation in western PA some years back that was turning disc-like copper pieces with autoloading lathes (Wasinos). Their biggest challenge was breaking up the birds' nests, which they finally accomlished after a lot of experimenting with feed rates and cutting angles.

-- Ed Huntress

Grant, I thought one could ball tungstens with just a piece of scrap iron. I will let you know if I ever cut it up.

Sounds yucky, the work would smell rather bad in a few days. (don't ask me how I know)

i

That really doesn't work. You want a metal that is as conductive as possible, both electrically and thermally. Short of precious metals, copper is the best you can do.

You can also use a chunk of copper as a backing bar for welds. I've used blocks of scrap aluminum for this too.

Grant

WOW, I'd sure like to look over your shoulder while you did this! I was trying to TIG weld some gussets into a box I made of .060" 3003 last night. I almost destroyed the box. I should have set up some copper bars to keep the aluminum from melting. My big problem was the gussets would melt into a puddle before I got any melting of the box material, even though they were the same thickness. I'm pretty sure they were the same alloy, but something else could have gotten in the scrap bin.

After painting it will look OK until somebody opens the box, then it looks like hell!

I've got steel, SS and even copper down just PAT, but aluminum still drives me crazy. I don't know why. (I have a Lincoln Square-Wave TIG

300, supposed to be a good machine.)

Jon

Very useful for welding thin aluminum sheetmetal corners without blowing holes. The copper bar stops blowthrus by acting as a chill. Lightly chamfer a corner on the copper bar to create a bit of space under the corner to be welded. You don't want the bar to chill the puddle right in/on the joint. Clamp aluminum pieces to bar with the chamfer under the corner to be welded. Weld away!

I make boxes by welding up pieces of sheetmetal, because I don't have a brake to bend them. Even if I did, with welding I don't have to worry about bending allowances to get the dimensions right.

It's even handy with thin steel sheetmetal, because weld-thru (excessive penetration) won't stick to the copper; it'll just reinforce the inside of the corner.

Don, it is a good point, something I did not think about (use of copper as backing for welding butts). At this point I already decided to keep this particular bar, but it is one more reason to.

i