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looking for someone that can machine copper pieces

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LAN_403

rp181

Thu Jul 30 2009, 09:34AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I have some .19" x 1.5"x12"pieces of copper that need to be milled to a .125" thickness, and then a 1.5" long section 1.625" from the edge milled down another .0625".
So the end product is a 12" long, 1.5" wide piece. Thickness is as follows:
8.875" of .125" thick
1.5" of .0625" thick
1.625" of .125" thick.

After that, The copper needs to be cut in half length wise, I can do that if you can't.

Proud Mary

Thu Jul 30 2009, 10:04AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I'm not too sure I understand the composite decimal-fractional notation, but that aside, you could easily grind these copper pieces down to the right size with abrasives if there are not too many of them, and it is important enough.

rp181

Thu Jul 30 2009, 10:41AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I changed it to all decimal =)
It is very difficult to sand something that thin. The copper gets hot very fast, and the end result is always bad. If worst comes to worst, I will modify the garolite enclosure. I don't want to do that, as I would have to use a table saw, with coarse teeth, and delamination could easily occur.

klugesmith

Thu Jul 30 2009, 10:07PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Sorry, got no milling service. And yes, Cu is hard to grind (and not easy to machine). Ever consider heavy duty etching?

Since your finished thicknesses are all multiples of 1/16 inch,
can you just build up your part from 2 layers of .0625 flat stock?
Or 16 gauge (48 ounce) sheet (thk. approx .0647 )

rp181

Fri Jul 31 2009, 02:40AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Would the etching work? It seems it would just etch down, and start etching on the sides, and below the masked part.

...

Fri Jul 31 2009, 04:50AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

If you aren't in a hurry I could do it at school, but it will be 2-3 months before I could get back to you. \

It seems like with the amount of work you do it might be worth it to invest in a cheep mill--you can get a small one from harbor freight for a few hundred bucks that would be able to do the job. You could even get away with a drill press and linear slide vice (something like

if you only need to do simple stuff.

rp181

Fri Jul 31 2009, 12:33PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I don't do very much work involving mills. My school has a nice mill, but no attachments. Its a new school, so woodworking took priority.

Buying the required bits would cost more than replacing the copper.

2 months is too long, I get a high spped camera in a month. If all else fails, I will try sanding...

Herr Zapp

Fri Jul 31 2009, 01:16PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

rp181 -

The first thing I'd ask is why your design would require stepped thickness in your buss bar? This just isn't good practice, and greatly complicates fabrication of the part. What can you change to eliminate the need for stepped thickness? If its a problem with clearance, can you form a offset in the part (a slightly raised bridge, etc) or shim something else to create the required clearance?

If your design is "locked in" and absolutely required stepped thickness, then here are some options:

I know you have already purchased some .19" thick material, but unfortunately what you've got can't be "easily" converted into what you want. From a machining standpoint, annealed copper is very soft and "gummy", and not easy to machine with cutting tools (eg by milling) or by abrasives. A file or belt sander can eventually remove material, but its a real PITA if much material must be removed. Especially difficult is the relative thinness of your material; holding thin, soft stock for any type of "machining" is quite difficult without making some special holding fixture.

If you need .125 thickness for most of your part, then start with .125 thick copper stock (a standard thickness) to minimize the amount of material removal required. If I understand your dimensioning, then there is only a small area that needs to be reduced in thickness to .062".

Another approach would be an additive process, where you use two layers of .062" stock soldered together where you need the .125" thickness. This way there is no need to remove any material at all. Copper is very easy to sweat-solder together if the pieces are flat and clean, and electrically this would be essentially equivalent to a single piece of .125 material.

You didn't specify what type of Garolite material you are using (linen reinforced phenolic? fiberglass reinforced epoxy?), but I wouldn't worry about delamination, regardless of how many teeth are on your saw blade. The phenolic-base Garolite cuts cleanly with a sharp carbide-tipped blade. The fiberglass-epoxy material is hell on any cutting tool, and will quickly dull even carbide tipped tools, as well as generating "sawdust" containing microscopic glass fibers that are very irritating to eyes and skin.

Regards,
Herr Zapp

rp181

Fri Jul 31 2009, 02:56PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

It is G-11, a epoxy glass garolite. These are for railgun rails, so the lowest part is for the insulator. The short .125" is bent 90 degrees, to exit the enclosure.

Thanks for the advice, I will just widen the grooves.

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