Joining copper sheet

Ah, yeah - warping. Soldering iron might be better in that respect.

Thanks, Bob

Thanks - I kinda' remembered that there was a copper-specific braze.

Bob

Thanks. I'm beginning to think that solder, hard or soft, is going to be a lot of trouble and maybe purely mechanical is the way to go. Copper pop rivets is my current favorite.

Bob

OK - like this:

\ / \ / \ \ / \ \ / \ \/ \/ or this

\ / \ / \ \ / \ \ / \ \ / \ \/

Oh, sure - the problem is that it's a closed space & you can't get inside to back up the spot you're working on. Jeez, that must be frustrating.

Temperature controlled is probably not in the picture, but I have a big electric iron that is at least 100w.

An iron is starting to sound a lot better than a torch.

Thanks, Bob

Thanks. That's something that I'd hadn't heard of.

Bob

...

It's obvious now that so many considerations are coming up: this should be researched. When we were thinking "We'll just solder this together" it seemed easy enough.

Thanks, Bob

I have two electric irons that were made for sheet-metal work. One is 350 W; the other is 300 W. You need a *big* iron to solder copper sheet. I've also used two or even three furnace-heated soldering coppers simultaneously for that work. The big electric iron is better for most of us.

As for the tensile strength of conventional soft solders, they run around

5,000 psi. Likewise for their shear strength, which, in well-designed joints, is the more likely mode in which they'll be loaded. High-silver and tin/silver solders made for work where food is involved can be stronger. Sn 95/ Sb 5 has tensile and shear strength of 8,000 psi +. You are not likely to approach that overall strength in copper, or even 5,000 psi, with mechanical fasteners, which load only a very small area of the sheet.

BTW, my uncle was quite expert at soldering copper stills during Prohibition, which he did to supplement his paltry salary as a shop teacher in public school. He made it clear to me that tinning was absolutely the way to go with any sheet-metal work that was more involved than a simple straight lap. Copper whiskey stills were soldered with lead-bearing solder by using double folds -- an especially tricky thing to solder, which was almost impossible to do without tinning the spots where you wanted the solder to stick.

-- Ed Huntress

Consider, too, that more heat causes more problems with warping. SilFos will be much more of a problem than soft solder in that regard.

-- Ed Huntress

You will have less problems with warping regardless of whether you use soft solder or brazing, if you insulate the work as best you can and get the whole assembly hot.

Dan

No, like a Y, so the seam can be squeezed or hammered shut. The ones you showed will warp and open up when heated and you can't heat both sides equally without smearing extra solder on the face of the metal. The iron tip itself doesn't transfer much heat, both it and the sheet have to be tinned so a substantial volume of liquid solder clinging to them can heat the work. This means you have to carefully consider where the heat needs to be applied before making the joint. On the folded seam you heat both pieces by pressing the iron into the depression that the solder will fill.

The type of joint you showed is quite ambitious and difficult for someone who has to ask how to do it. It's possible to melt the flanged edge on both pieces back to the hammered shape with a torch or TIG and file the edge smooth but you need the skill to be able to fill accidental holes. I can barely do it on auto body steel, I wouldn't try copper without practice.

Otherwise the two halves could be carefully fitted dry, tinned, then weighted and reflowed in an oven.

If you don't like the appearance of the flat folded joint you could try an upright flange on both pieces so they snap together like an aspirin tin. The advantage is that you can adjust the edges in and out to match each other without disturbing the sculpted curves as much as attempting to make the edge of both pieces fit flat would do. Warpage will make the width of the joint vary but that isn't too noticeable from a distance. Use a few sheet metal screws to hold it together during assembly, solder can easily be dragged across small holes.

If you are only trying to hide the solder you could tin the inside of oversized flat edges on both pieces, clamp short areas together and solder them at the outer edge, then trim the edge back clean. The joint is unlikely to be continuous and watertight so leave a gap at the bottom to drain it.

Seams across a surface aren't as difficult as they look. Fold both edges and hook them together, pound them shut, then flatten the good side against an anvil with a 'seamer', a punch with a shallow rectangular groove milled across the end. For one-off jobs I've clamped three thick plates in the vise with the middle one lowered and hammered the sheet metal down onto them. That was to form louvers on a curved surface for a stainless steel cat-con heat shield, but the idea is the same.

jsw

100w seemed small to me, but I thought that Jim meant that he had used 100w iron on copper sheet.

True, but this IS a weathervane - how much strength could it need (famous last words). Or, we could could the rivets to get it assembled & then solder.

Cool uncle.

Thanks, Bob

You don't know the half of it. His other part-time job was wrenching the three Liberty aircraft engines on the Fleur de Lis, a 55-foot-long rum runner that was clocked at over 50 mph around Sandy Hook, with a hold full of booze. Empty, she was off the charts, and the Coast Guard never had a chance.

Then he became the head of the New Jersey Industrial Arts Education Association.

-- Ed Huntress

Bob Engelhardt fired this volley in news: snipped-for-privacy@news2.newsguy.com:

Just don't confuse it with "anti-Borax", which IS a strong flux, not a mask.

LLoyd

I have copper gutters, and they are soldered.

I have also had houses with soldered copper window pans in a bay window, intended for flowerpots, so watering the flowers wouldn't rot the wood.

Soldered copper is the traditional way to fabricate flashing for windows as well. Since the time of the Romans.

And weathervanes have been made of soldered copper sheet forever. Here the issue is making sure that the constant motion doesn't wear the bearings out too soon. A piece of brass soldered into the copper may be a good idea. I would also make sure that the vane cannot be lifted off the vertical pole by any reasonable storm wind. The definition of reasonable is whatever will cause the wing to fly away, probably 150 to

200 mph.

I would not worry about the durability of soldered copper, indoors or outdoors.

Joe Gwinn

You need a heat sink between the joint you're soldering and the previous joints. Maybe a couple of pieses of scrap copper, or even aluminum, clamped around the metal near the joint, to absorb the head and dissipate it before it melts the other joints.

Good Luck! Rich

Me, too! ;-)

Cheers! Rich

even a cold rag would do it

For large chunks of sheet, a large soldering copper is hard to beat. I inherited a bucket full. The old-timers used to use kerosene or gasoline blowtorches to heat them, most of the torches had a rest for the copper's shank. A propane torch could be used for heating, given a solid rest for the iron. Makes even a 300 watt iron look sick. But the user has to know when to clean them, when to tin them and everything has to be just so. Got to have a tinning block, too, a cube of ammonium chloride, for tinning the irons. Tinning the work beforehand is almost mandatory, the only time I've gotten away without it is when using some patented solder paste that had powdered solder in with the flux. Worked well but was expensive. Both surfaces have to be absolutely clean and shiny, whatever method is used for soldering. No fingerprints, either.

For stop-off, I've used a talc stick like the welders use for marking out, works fine. Read about that in Brownell's Gunsmith Kinks.

Stan

.to be absolutely clean and shiny, whatever method is used for

I'm old enough that I had to use coppers to solder my tin cup in 7th-grade metal shop class.

I sold my last ones at a yard sale a few years ago. So far, I haven't regretted it.

Same here. I have a bunch of them, and I've used them for that purpose -- another trick taught to me by my uncle.

-- Ed Huntress