[Woodworkers] Copper metal working

Fri Apr 16 16:03:19 PDT 2021

Richard and all,

   Follow-up on the copper sphere:

   I drilled the sphere and did fine. But my first question is what is the proper drilling rpm for copper? Everything I’ve seen on the internet (9/64” drill bit) says 3000 rpm. That just seems fast to me. I ended up drilling at 1200 rpm and did fine (using 3-in-1 lubricant). But should I have used 3000? I will be doing more.

   I threaded the sphere and a steel rod and screwed the rod into the sphere. I mounted the sphere on the lathe and used the tail stock to start but will eventually have to back off the tail stock. I used an Easy Tool scraper and started to turn the sphere. It was a little wobbly as I’m sure I didn’t hit the exact center of the sphere. When I gently entered the cutter to the sphere I got small chips and a lot of noise (I’m sure because metal on metal and a little wobble). I stopped turning because a 3 oz ball of metal coming off the lathe makes me nervous and decided caution was the better part of valor so I could seek more advice. The lathe was turning around 1200 rpm. Faster, slower? What type of chips should be coming off? The DP created longer wisps of copper and I was hoping for the same at the lathe but probably not realistic. What did cut was very rough. Sound normal so far?

   I had safety glasses and a face shield on and I know wood coming off a lathe can do damage but when I think of this sphere all I can see is a big bullet ☹. 

   What do you think? Soldier on? 

Chuck

From: Richard Allen <rla_buy at yahoo.com> 
Sent: Tuesday, March 30, 2021 4:19 PM
To: woodworkers at sawdusters.org
Cc: chuck.steger at gmail.com
Subject: Re: [Woodworkers] Copper metal working

I have turned copper on a wood lathe before.  I would take a 7/8” rod about 2” long an turn a sphere at one end.  The end being held by the lathe could be turned down to a suitable diameter so the sphere would be attached to the rod as a single piece of copper.  Another option would be to drill and tap the 1” sphere and thread some of your 3/8” rod to screw into the taped sphere.  Copper drills fine.  Plan on discarding the drill bit as sometimes the copper will “weld” to the drill bit.  I would do the drilling with the 1” sphere in a chuck on the lathe.  I would turn down the 1” sphere by mounting the 3/8” rod in a chuck on the lathe.  Copper turns with a scraper.  It is a fairly slow process but 10 minutes of scraper work and 15 minutes of sanding and polishing should give you a sphere shape to your likening

On Mar 30, 2021, at 5:02 PM, chuck.steger--- via Woodworkers <woodworkers at lists.sawdusters.org <mailto:woodworkers at lists.sawdusters.org> > wrote:

Hope everyone is safe and healthy!

   I need some advice on working solid copper. I’ll give you some context on what I’m doing.

   I designing and building a Heritage Box for someone. Everything that goes into the design and construction will have some elements from their cultural background. Their mother and grandparents lived and worked in a copper mining town in Chile and copper was a big part of their lives. To bring copper into the design, I will attach the legs to the box using copper rods. Since the legs taper, I will use 1/8”, 3/16”, and ¼” rods and leave a ¼” gap between the legs and box. But this is subtle and I wanted to add something else. So I want to add a copper sphere at the top of the box. I drew up the design full scale and the sphere looks good at ¾”. So, I started researching copper spheres and what I found are jewelry spheres ½” and less or solid spheres 1” and greater. I ordered the 1” spheres which are actually used for plating copper.

   So here are some of my issues/questions/concerns:

*	Is there any way possible to reduce the diameter? I thought about some kind of holding contraption on a lathe and then using files but that just sounds like a bad idea.
*	The sphere weights in at 3 oz. Now that may seem light but it’s a little heftier that I wanted because I don’t want it to tip the box over when hinged open. The box footprint will be 8”x12” so it may be OK. I will build a prototype as I always do so I’ll find out. Also with a prototype it will be easy to see if 1” is too big. A ¾” hollow sphere would be perfect but I can’t find that.
*	Will solid copper drill OK? I would like to drill a hole for a rod to anchor the sphere to the box. I will epoxy the sphere to a cradle but a rod would be so much more secure IMO. And, given the weight, I would feel better.
*	Here’s another take …. Is there a way to cut the sphere in ½” I only have WW bandsaws so even with a metal blade, WW bandsaws run too fast, don’t they? The thought process here is maybe I take the two half spheres and attach them to the side of the box as an adornment. The design will be mostly Asian so spheres might look good. 

   So you can see the design is in total flux. I’ve started building the prototype out of pine.

Chuck

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