How to Weld Together a Copper Goblet
When we join him, Kevin is welding the base to the stem of the copper goblet. The copper is red hot. He'd turned the parts of the goblet on his lathe a year ago, and just got tired of seeing it sitting around. He was using his Everlast POWERTIG 255 EXT TIG welder for another project and thought, "What the heck, let's crank it up to max and play with a little copper."
Kevin says you have to have all that amperage when you're working with copper because it's a great heat sink. After all, conducting electricity is its job. That's why it makes great frying pans, etc. So you really have to hit it hard. Kevin had the 255EXT's foot pedal the way to the floor with the machine set at 255 amps.
He tried using his little propane torch, but that didn't get it anywhere close to the temperature he needed. He thought about using his oxygen-acetylene unit, but didn't have enough hands while working alone.
He used the propane torch to heat it up a little, then use the TIG torch at 255 amps to heat it to welding temperature. Kevin says copper acts a little like aluminum. It takes a lot of heat, and then all of a sudden you're welding.
As an example, Kevin shows a piece of 1/4" copper plate he was using to set his settings. He tried welding with AC instead of DC to see what would happen and found out, "Don't do that."
He was welding along, playing with the pedal to figure out how much amperage he was going to need and how to control the puddle. He got right to the end and blew a hole through the copper plate. When the molten copper dropped through and hit the relatively cold steel table, it froze. It created a small pocket that Kevin then filled in.
The copper Kevin had welded looks nearly black because of the oxide that formed while he was welding it and the fact that it wasn't completely protected by the shielding gas. If he'd rinsed it in the sink while it was still red hot, the oxide would have washed right off.
Kevin says he's a little handicapped, actually, because he doesn't have any tri-mix gas. He just has an argon-CO2 mix. If he had an argon, CO2 and helium mix, he'd have had almost double the "horsepower" to weld the copper - about 1.7% more amperage than is listed on the dial. He'd have a lot more amperage to get it hot quicker, control it better, and get a better weld.
On the goblet, he's trying to get a big enough fillet so he can go back to the lathe and turn it to get a nice, smooth even connection between the stem and the base. It would look - and actually be - machined. It would look like it was all one piece, better even than a beautiful weld.
Kevin will then weld the bowl of the goblet to the stem. He needs to clamp it to make sure everything is straight and true, because he needs to turn it on the lathe to get those nice smooth connections and he doesn't want it wobbling.
Next Kevin takes the copper to the sink and rinses it off. Steam rises, not dangerous fumes as if he were cooling some other metals, like bronze. Caron then uses the wire wheel to clean the base and stem.
Then Kevin talks about what he uses for welding wire. He shows the heavy gauge copper wire, which is actually just repurposed Romex electrical wiring. He cut off a chunk, stripped off the insulation to give himself a nice, heavy gauge copper wire.
Finally, Kevin shows the finished goblet.
At the end of the video, Kevin learns a lesson of his own ....
Watch more videos now