[TheForge] Working copper

Tue Mar 12 08:34:00 2002

Morning, Folks

You folks are such a great source of information and I greatly appreciate 
that which has been offered in the past. In similar fashion I wonder if I 
might solicit a bit of advice on working some copper.

I have  volunteered to make a couple things for the Mastermyr exhibit at the 
ABANA conference and finally getting to it. To wit: a cauldron and an adz. No 
problem with the adz but the copper cauldron is a bit more difficult than I 
anticipated. There is one particular aspect of it that I am unsure about and 
I would like to stay as close to a 1000 year old Viking production technique 
as possible. But I would like to know what is the current technique, also.

It has to do with what I know as 'cramping', the joining of two edges 
together. The way I do it is to thin or scarf the edges of both ends to be 
joined back about 1/4". Then I file or sand it smooth and clean. Then on one 
edge I cut cramps or slits that go back as far as the scarf, about 1/4". 
These, then are tabs that can be alternately bent up and down. The other 
scarfed edge is inserted between them, the tabs are knocked down and the 
joint fluxed and soldered. 

The question is this: I have had some tell me that both edges need to be 
cramped or tabbed. You do one edge and then place it on the other and mark 
and cut matching tabs. This GREATLY adds to the time, difficulty, etc., of 
making a joint. I think this is unnecessary. My single cramped joints seem to 
be holding well and I can usually flatten and bend them on the anvil with a 
hammer. (Up to a point)

Can anyone share their experiences or recommendations with me on this 
process? Also re prep for soldering. The cauldron is thin, being made of 
about .020 copper and is about 20" in diameter with six separate pieces used 
to make up the sides and thus require this edge joining. 

Also, could someone make recommendations re flux and solder for this joint? 
All I have around is some Stay-Clean flux and some Canfield no lead solder. 
But I am beginning to suspect that some lead solder might be better.

Kindest thanks for any help

Don Plummer
Phoenixville, PA