[TheForge] Working copper

[theforge@mailman.qth.net]

Hi Folks, and thanks again for the suggestions re joining (cramping) copper 
sheets. 
I thought I might share my experiences in the event anyone else gets involved 
in something similar. 

As a reminder, I am trying to replicate a cauldron that was a part of the 
Mastermyr find that is described in the book Norm Larson republished titled 
"The Mastermyr Find". The intent is to have these items displayed at the 
LaCrosse Conference. 

If Rob Fertner is listening in, perhaps he might want to re-send the written 
piece about this project to theForge. There may be some new members not 
familiar with this effort. 

The original cauldron was 49cm in diameter, 20.5 cm high and made up of six 
pieces of varying width that were all about 0.05cm thick. I interpreted that 
to be 19-1/4" by 8" by .020. Because of the scrap I was working with, one of 
the joints is about a 60 degree angle. 

I tried joining the pieces by each of the varying techniques suggested below. 
In each case the edge was sanded or filed bright, hammered to a sharp scarf 
about 1/4" wide and sanded again. Using a cotton swab I applied a coat of 
sparex disolved in water. This was later rinsed off. The various techniques 
were:

1.  Cut cramps about 1/2" wide in one edge only and tapped them down firmly 
over the other edge with a hammer and on an anvil face. Cramps, as Jerry 
said, look like dovetail joints. But dont make the dovetails real pronounced. 
Fluxed from both sides and ran a solder joint.

2.  Cut cramps on one edge but 'tinned' the other edge before clamping them 
down and fluxing and soldering.

3.  Tinned both edges, then cut cramps on one side and fluxed and soldered.

4.  Cut cramps on both edges. I did this by clamping the two edges together 
and cutting the cramps on both of them at the same time with the airplane 
shears. When you do this and interconnect them it makes a wonderfully strong 
mechanical joint. I found that when you flux them you have to wiggle and tap 
them to make sure flux permeates those tight joints. 

5. Flux one edge and then clamp together and cut both cramps and join, flux 
and solder. 

In the end, I am not able to see any difference in any of the joints. They 
all seem to be holding very well and will tolerate quite a bit of flattening 
with hammer on anvil. In fact, you can just about flatten them until the 
joints are the same thickness as the copper stock.  I guess if I was in a 
production mode I would go with the fastest and simplest. 

Kinda fun doing something different once in a while. Now I gotta see about 
getting a bottom in it. 

Regards to all

Don Plummer
Phoenixville, PA