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Thread: Silver soldering question
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27th Mar 2016, 02:18 PM #1Senior Member
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Silver soldering question
Let's just assume a hypothetical : I want to silver solder a 1/2" pipe into a home made brass fitting. Should I make the fitting a press fit to the pipe ? or should there be a gap to allow the silver solder to penetrate ? and if so what size gap ?
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27th Mar 2016, 02:30 PM #2
Small gap. Silver solder will "wick" into pretty narrow spaces, but leave a slight space to ensure full coverage. As long as the 2 can slide together without pressure should be fine.
Dean
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27th Mar 2016, 04:55 PM #3
As Oldneweng said, get it nice and clean and use a bit of silver solder flux. Silver solder is very forgiving.
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27th Mar 2016, 05:27 PM #4
Fitting/pipe should be able to be pushed in with very little resistance by hand, if you have to use force, it's too tight.
Cheers
DJ
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29th Mar 2016, 08:38 AM #5Senior Member
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Ok thanks.
Yesterday I needed to make an internal threading tool. I silver soldered a short piece of 1/4" HSS onto some 3/8" bar, then while I was grinding it the tip fell off.
When it comes to electrical soldering I am A1 but I always seem to have trouble silver soldering things. I usually get what looks like a dry joint.
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29th Mar 2016, 09:14 AM #6Most Valued Member
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Not enough heat by the sounds of it.
what silver solder % are you using. Steel/steel or steel to copper/brass should be 45%.
Copper to brass should ideally be 45%, but you can use 15%...I use 15% on brass to copper as its more forgiving..ie less likely to overheat. 45% is easy to overheat
Paint you flux onto joint before you heat. Heat gently and watch for first sign of solder wanting to melt and hold at that temp. Slight carburising flame is a more gentle flame for beginners as it allows one to pull back when too hot.
Dont boil your solder.
Flame must be hot enough to heat decent area of work without overheating it.
If work is any shade of yellow/red its too hot!!
Like all soldering, solder will flow with the heat...or should I say to the heat.
penetration can only be achieved if all the joint is hot enough.
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29th Mar 2016, 09:26 AM #7
One more point is to watch for the solder to wick into the joint. Just put solder on at one point. If hot enough the solder will wick into the joint. You should be able to see this. As Eskimo says, flux on the joint. All over both sides and clean the surfaces first then don't touch them with fingers.
I have to admit that most of my knowledge about this is from YouTube.
Dean
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29th Mar 2016, 10:33 AM #8Senior Member
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I don't understand. The silver solder won't melt onto the surface if it's not bright red hot (more like pink really). and How do you not boil the flux ? it does that when it dissipates the water contained in the flux.
The job at the moment is high speed steel to mild steel.
I'm using 15% rod and Ezi-weld 602 flux. Also using a propane torch.
P.S. Just realized you said "don't boil your solder". I didn't read carefully enough.
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29th Mar 2016, 11:03 AM #9Most Valued Member
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I said dont boil the solder.
You shouldnt have to get it red red red hot. It should just be bordering on a very dull red.
brown tip (15%) (or less) is not recommended for ferrous metals.
It should be >30% or even bronze for steel.
I use 45% blue tip as that is what I must use for work
Brazing temp for complete fluidity for 45% SBA245 is 625c
bt for 15% SBA115 is705c
bt for 30% SBA230 is 715c
There are also some others that one can use such as SBA330T but they have higher temps ie 765c
also my experience with brown tip 15% on steel is this:
While it can appear to work it is also prone to failure...vibration appears to weaken it rapidly.
It, the brazed joint, always looks messy!
I'd be hung out to dry if it failed on a steel joint that I did and injuries occured to someone as a result!
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29th Mar 2016, 11:30 AM #10Senior Member
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29th Mar 2016, 11:36 AM #11Most Valued Member
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29th Mar 2016, 12:07 PM #12Most Valued Member
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Silver solder can take sometime to heat up, If you're holding it out of the flame then touching it against the joint you might think its not hot enough.
Depending on the joint you can beat the silver solder flat and place it between the pieces to be joined, then heat. (you can buy silver solder sheet to save you the hammer work).
Stuart
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29th Mar 2016, 01:47 PM #13
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29th Mar 2016, 01:51 PM #14Senior Member
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I rang a plumbing place a while ago. They didn't have anything higher than 15% but they told me about a local gas place. I ended up getting a stick of 45% for $12.
I also watched a couple of youtube vids. One of them showed a guy using flat solder. By watching them, I think maybe I have been putting the flux on too early.
I'll see how how I go when I clean it up and try again.
By the way, on another project, will silver solder stick to gal ?
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29th Mar 2016, 02:04 PM #15
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