The Shop > Metal Stuff
First time brass brazing
awemawson:
The 'Heating and Ventilating' chaps when installing air conditioning use a phosphorous copper alloy that needs no flux. I got some years ago when I was making up fittings for my 100 kW induction furnace that needed water cooling pipes plumbing in.
I was sure that I still had some, so as I had a break between lambs arriving this morning I thought I'd do an experiment with it before I recommended it to you - so here are the results.
The stuff I have is 'Harris Phoson', but there are many brands of the same thing:
http://eu.harrisproductsgroup.com/en/Products/Alloys/Brazing/Phos-Copper/Phoson.aspx
Not having 1" brass stock nor 4 mm bar I sliced a bit off a 20mm hexagonal bar, and also turned a 1/4" hex brass bar down to 1/4" round and cut an inch off the end. Then I drilled a small recess in the 20mm hex for the 1/4" round to sit in to give it a location.
wgw:
Have you drilled a hole in the flat, or you trying to butt the rod to the flat. I don't think a butt will be strong enough. At these sizes a propane torch should be ample with the correct solder and flux.
awemawson:
Then with it sitting on a fire brick, with a carbon rod balanced on top to stop it blowing away, I heated it with my Rothenburger propane torch and applied the Phoson strip to the joint on the far side away from the flame. It flowed nicely but I put far too much on!
Then I cleaned it up, and to prove that it was a sound joint, mounted it in the lathe, skimmed the rod down to 6 mm and ran an M6 die down it.
awemawson:
Now the point of the exercise was to show if only a slight location dimple was going to give enough surface area for a sound joint. And it was. The forces on the 6 mm bar when turning would have broken off an unsound joint, and then running a die down it would have been the last straw.
But the fact is it is a very sound joint - so yes I recommend this Phoson stuff as very easy to use. However I do vaguely remember a caveat from years ago not to use it in steam boilers - can't remember why.
awemawson:
Probably worth noting that I deliberately did NO cleaning of the brass before brazing - it was straight off the lathe. So although it was fairly clean it would have had some oil on the surface
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