I want to make a garden
trellis or two and darbor out of common copper plumbers pipe
(1/2", 3/4" and 1"), but I don't like the look of the fittings. I
am needing 90 deg and 45 deg joints as well as tees.
G'day'; I believe you have two options, both of which will require
you to make a visit to your local welding supply shop. You can't
really actually weld copper without special equipment and
1); Brazing. This is done using filler rod of a special brass
and is available in several thicknesses, but I suggest that 1/16th"
rod/.wire is what you need. You also need a flux. Now borax will
do, but the fluxes that are commercially available for brazing are
better. Copper is notorious for oxidizing on the surface when
strongly heated, and a good flux will dissolve the oxide as it is
formed and will keep the surfaces clean to obtain a good flow and a
strong joint. You will need a good torch with a very hot flame,
and I recommend oxygen/propane, though many plumbers use an
air/acetylene torch. Copper is a good conductor of heat; almost as
good as silver, so that is why a really good hot torch is
necessary. The pieces to be joined must be held together in some
manner (I use a chemistry 'retort' stand and clamps) but they
don't need to be the perfect fit that silver solder demands; brazing
rod is a gap filling material, and part of it's strength is obtained
by the joint having a build up of 'fillet' metal. The brazing rod is
applied as necessary to achieve a good joint, as in lead soldering.
The rod is heated then dipped into the particles of solid flux which
will adhere to the hot rod before being applied to the job. The
technique is not difficult, but a little practice will be necessary
for a newcomer to brazing. The metal needs to flow to a liquid, so
a technique of being able to control work temperature by moving the
torch about as necessary will soon be acquired with practice. Wish
I could show you! The main 'secret' is getting the job hot enough,
clean enough and keeping it hot enough for the metal to flow
easily, but only where it is wanted. Brazed joints are very strong,
but there is one small problem; to get the joint hot enough to do
the job will soften and anneal the copper at that point. When the
joint is completed, hot water and a stiff brush will get rid of
remaining flux. It may also be pickled in sodium bisulphate pickle
as used in silver soldering, to remove oxide. You will need to
braze a disc to the end of the pipes, but drill a tiny hole in the
pipe to let out expanded air and steam. I have made large aquariums
by brazing together a rectangular frame of angle iron , and they
seemed almost as good as welded ones for that purpose.
2) 'Silphos' This an alloy rod containing a little silver, brass,
and phosphorus which is applied to the joint as in brazing, except
that it does not need quite such a high temperature, but almost so.
Plumbers use this all the time in New Zealand when plumbing a house
with copper pipes, but it isn't as strong as brazing. It doesn't
need to be, as house plumbing doesn't suffer the stresses that your
furniture would. This material is also gap filling, but a
negative thing about it is that the joint appears a dark, dirty
grey. This doesn't matter with plumbing as the pipes are usually
hidden. Incidentally, modern houses are plumbed with black heavy duty
polythene piping; copper has gone out of fashion.
For cutting the copper tubes, I suggest you get a cheap mitre box
from your local DIY store, and use a 'G" clamp to hold the pipe in
place whilst cutting with a fairly fine toothed hacksaw. Remember,
as with jewellers saws, at least two teeth must always be in contact
with the metal. Use a bit of candle as a lubricant on the saw.
If you need to file the copper, give the file a squirt of WD 40 or
CRC555 to stop it clogging. Even kerosene will work.
Please let us know how you get on.
Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ