bending copper for a tabletop

[John Daake]

I know this is outside the topic of woodworking, but I was given a 55 x 55 inch square of what he calls architectural copper, used for the back of water features, for table tops, etc. I recently saw some round tables with copper sheet tops that looked really nice, but I don't know how I could bend the copper around the table edge without getting folds or possibly starting cracks in the metal. Does anyone have some experience with this, or should I stick to rectangles?

[Ken Fitzgerald]

John,

We don't allow double posting of the same thread. If you don't get some answers here shortly, I will move this thread to the new Metalworking Forum where it really is more appropriate.

[Ken Deckelman]

The round tops you saw where probably stamped/pressed out of a sheet, there is no real way to do that in a home shop.

[Stephen Cherry]

Metal working is fun, and I used to have some interest in it. check out some videos on "metal spinning" on youtube. If you do have a big lathe, one thing to try would be to spin the table top on the outboard end of the lathe. You would need to contact cement the metal to the plywood top, and then spin it around the edge.

[hank dekeyser]

Well you could always treat it as a laminate - and edge it first, then do the top, trim it - then go back and solder the seam ? All kinds of options, being that copper is such a soft malleable metal.

[Chris Fournier]

When copper is heated to cherry red and allowed to cool slowly it will be annealed. In the annealed state copper will be very maleable. If you continue to work the copper it will eventually become work hardened and you'll have to anneal it again. There will be discolouration etc etc so I think that you would need to do some testing to see if annealing will work for you. Perhaps there is a heat treating company near you that can do the entire sheet at once for you.

[John Daake]

Thanks for the suggestions, guys. I think I'll take a small sample of the material and experiment with heating it.

[ian maybury]

It's possible to work fairly ductile materials like copper by tapping it very gradually around a form using a hammer - the effect is very similar to the metal spinning that Stephen mentions. Care is needed to avoid leaving hammer marks everywhere. It'd be necessary to anneal it fairly frequently to re-soften as Chris says - I know from experience that copper work hardens very quickly.

There is the odd copper smith around that should be good at this sort of thing who could advise or even help with the work. Some of the custom car builders and the like use similar techniques, or machines that use the multiple small 'taps' method too.

I guess the awkward part is that you would ideally have enough copper to run a few trials. Another issue could be that if the the material you have has a textured surface you would loose this in the worked area. Spinning might do the least damage in this regard....


ian

[John Sanford]

One thing to remember about the hammering is that hammered copper is often a design element, so a hammered surface isn't necessarily a bad thing.

[Stephen Cherry]

It's possible to work fairly ductile materials like copper by tapping it very gradually around a form using a hammer - the effect is very similar to the metal spinning that Stephen mentions. Care is needed to avoid leaving hammer marks everywhere. It'd be necessary to anneal it fairly frequently to re-soften as Chris says - I know from experience that copper work hardens very quickly.

There is the odd copper smith around that should be good at this sort of thing who could advise or even help with the work. Some of the custom car builders and the like use similar techniques, or machines that use the multiple small 'taps' method too.

I guess the awkward part is that you would ideally have enough copper to run a few trials. Another issue could be that if the the material you have has a textured surface you would loose this in the worked area. Spinning might do the least damage in this regard....


ian


One thing about hammering is that it is pretty tough to shrink the metal, whereas with spinning the metal basically is stretched around a form.

Here's a video with the techinque:
http://www.youtube.com/watch?v=7RD_8pWTZ5A

I think that a round plywood table could be wrapped mounted on the lathe ( or turned), and the copper glued to the flat part and spun around the edges. make sure that the edge is softened otherwise it would be a giant meat slicer. Just my thought.

[Carroll Courtney]

If the copper is thin enought,you could use a vacuum press.Maybe take some masking tape and tape up the edges so that not to punch a hole in the bag.Just a thought---Carroll

[Jon McElwain]

You might try posting this at the forum http://allmetalshaping.com. The forum is similar to the creek, but for metal shaping. They deal in exactly what you are trying to do.

[John Daake]

Actually, as a couple of you mentioned, the tables I saw used the hammered look in the copper as a design element -- maybe to disguise the marks made in wrapping the edges. The Youtube video is pretty cool; while I don't have a large lathe, I know someone who does and who might consider this an interesting experiment. I'm also going to post the question at the metalshaping website just to see if the suggestions run similar to what you all have come up with. Thanks for the input.

[Perry Holbrook]

I work with copper for my little boxes. The copper you have is probably 16 oz material, it's used for gutters, flashing, etc. That's a little thin for spinning. The you tube guy is doing something that is for an experinced spinner. I've done some basic spinning and would never dream of spinning something as large as a table top. That is a job for a Very experinced spinner, if even them.

The copper will anneal at about 1100 deg F. Not cherry red but a dull red. It does not need to cool slowly, quench in water. Be sure to anneal as soon as copper becomes hard to move, it will crack if you don't. Anneal as often as necessary.

Hammering over steep angle, especially a large diameter one, will be difficult. I might suggest a design with an angled edge, still tricky but do able.

Good luck.

Perry

[Larry Edgerton]

I make a lot of copper flashings in my restoration work. That would be a tough one for me. When I make round flashings I bend them on the brake and use a shrinker/stretcher to form the curve by manipulating one side of the angle with the stretcher. But this would not work in your circumstance, unless you forned an angle into the curve and soldered it to the flat circle. Still, the stretcher leaves marks on the copper.

I would like to try spinning once, that would be interesting. Some day I will try it on the lathe on a small scale.

[Ryan Baker]

When you wrap down around the edges, you will get lots of wrinkles, as you mentioned. You have to shrink the metal to get it smooth again. That takes a lot of work and metal finishing skills. It also requires a shrinker or power hammer, unless you have infinite time. Metal spinning it doesn't sound like an option unless you have some serious equipment and a lot of spinning experience.

[Tom Grant]

And now for something completely different...
What about covering it with several (4 - 20) pieces in an interesting geometrical or random pattern? This would allow you to easily compensate for the edging fold-over, and the joints could be folder & hammered, soldered or even riveted. You could even color (lots of ways with copper) or texture some of the pieces differently. It could be a really cool looking piece.

[Larry Edgerton]

And now for something completely different...
What about covering it with several (4 - 20) pieces in an interesting geometrical or random pattern? This would allow you to easily compensate for the edging fold-over, and the joints could be folder & hammered, soldered or even riveted. You could even color (lots of ways with copper) or texture some of the pieces differently. It could be a really cool looking piece.

I just had a bay window roof done last year and that is how the subcontractor did it. He made copper copys of the original turnmetal sheets that were on the roof for 130 years. That would be an interesting top design, better than one sheet I would think. Google turnmetal roofing and you should be able to find information on how it is done.

You would still have to deal with the curve, but in smaller sections. I made a couple of things in hammered copper, which may be your only viable option. Man it takes a lot of hammer strikes to do a area. I just remember that my forearm felt like it was going to fall off.

[Jeff Caskie]

We have a round copper top table that we love. Looking at it closely, I see a seam around the round edge which would seem that they edge banded it with a strip of copper rather than bending the top over. It looks like they did bend the top over a bit (1/8-1/4") as the seam is down a bit on the side... which helps it blend better making the seam less visible.

[Charles McKinley]

http://www.lindsaybks.com has several books on Metal Spinning. You HAVE to get the catalog to see all of the books he has to offer. The catalog is very interesting. The Dave Gingey quote in my sig line comes from the Gingery books that he offers.