Tig brazing over Tig welds for for a little razzle dazzle.
#1
Senior Member
Thread Starter
Tig brazing over Tig welds for for a little razzle dazzle.
So, a little bit of background is that I'm a welder,went to school for it, certified in carbon steel,stainless steel and aluminum. Been working and Tig welding 6000 series aluminum for the past few years. I have a frame that isn't a big deal(KHS Urban X), I got a powder coater I helped out when he needed to get some jobs done quick and I can get it done for cost of powder.
What I was thinking was I would Tig braze over the welds and polish the frame and powder a candy color over it so that the braze being a different color than the steel would shine through Are there any problems I might encounter?
This is purely for looks.
What I was thinking was I would Tig braze over the welds and polish the frame and powder a candy color over it so that the braze being a different color than the steel would shine through Are there any problems I might encounter?
This is purely for looks.
#2
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
I'm TIG brazing with silicon bronze over TIG welds on steel for a project I'm working on now where he wants a "raw" finish. I'm going for the look of a fillet brazed frame, but I only have/know how to use the TIG. Silicon bronze on its own might be strong enough but I don't want to chance it.
The process works well. The hard part, that needs a lot of practice and patience, is filing down the fillets. A "dynafile" or "finger sander" can be used where you can reach things without gouging the actual tubes. In tighter spots you need to use hand-files, which actually aren't much slower at removing material, just harder work. So as with anything I'd try it all out on a couple of bits of scrap first.
The brazing does put a bit of heat into the tubes. It melts at a lower temperature than steel but it's still a big chunk of red-hot copper you're wrapping around those joints, so watch out for distortion. Bolt a bit of threaded rod securely between the dropouts to hold them at the correct spacing and leave it there throughout the process. Space your work out-- do a bit on each joint at a time before moving to somewhere else on the frame while it cools down, and recheck the alignment when you're done.
The process works well. The hard part, that needs a lot of practice and patience, is filing down the fillets. A "dynafile" or "finger sander" can be used where you can reach things without gouging the actual tubes. In tighter spots you need to use hand-files, which actually aren't much slower at removing material, just harder work. So as with anything I'd try it all out on a couple of bits of scrap first.
The brazing does put a bit of heat into the tubes. It melts at a lower temperature than steel but it's still a big chunk of red-hot copper you're wrapping around those joints, so watch out for distortion. Bolt a bit of threaded rod securely between the dropouts to hold them at the correct spacing and leave it there throughout the process. Space your work out-- do a bit on each joint at a time before moving to somewhere else on the frame while it cools down, and recheck the alignment when you're done.
#3
Senior Member
Thread Starter
I'm TIG brazing with silicon bronze over TIG welds on steel for a project I'm working on now where he wants a "raw" finish. I'm going for the look of a fillet brazed frame, but I only have/know how to use the TIG. Silicon bronze on its own might be strong enough but I don't want to chance it.
The process works well. The hard part, that needs a lot of practice and patience, is filing down the fillets. A "dynafile" or "finger sander" can be used where you can reach things without gouging the actual tubes. In tighter spots you need to use hand-files, which actually aren't much slower at removing material, just harder work. So as with anything I'd try it all out on a couple of bits of scrap first.
The brazing does put a bit of heat into the tubes. It melts at a lower temperature than steel but it's still a big chunk of red-hot copper you're wrapping around those joints, so watch out for distortion. Bolt a bit of threaded rod securely between the dropouts to hold them at the correct spacing and leave it there throughout the process. Space your work out-- do a bit on each joint at a time before moving to somewhere else on the frame while it cools down, and recheck the alignment when you're done.
The process works well. The hard part, that needs a lot of practice and patience, is filing down the fillets. A "dynafile" or "finger sander" can be used where you can reach things without gouging the actual tubes. In tighter spots you need to use hand-files, which actually aren't much slower at removing material, just harder work. So as with anything I'd try it all out on a couple of bits of scrap first.
The brazing does put a bit of heat into the tubes. It melts at a lower temperature than steel but it's still a big chunk of red-hot copper you're wrapping around those joints, so watch out for distortion. Bolt a bit of threaded rod securely between the dropouts to hold them at the correct spacing and leave it there throughout the process. Space your work out-- do a bit on each joint at a time before moving to somewhere else on the frame while it cools down, and recheck the alignment when you're done.
As far as finishing the braze,I thought that maybe since it's softer metal I could make it look just like a weld,stack of dimes like.
#4
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,003
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4172 Post(s)
Liked 3,792 Times
in
2,271 Posts
As mentioned the trick is in the results. Meaning practice until it's easy to finish with the look you want. Industry has filleted over welded tacks for decades. In this case the tack is REALLY big Of course that the tubes have now gone through two major heat cycles... might be a concern for more temp sensitive tubing.
A note about primerless finishes. It's well known that power paint is porous at the microscopic level and water can and will attack the steel. Wet clear coats also are well known for rusting, often at the cable stops, drop outs and the BB and headset faces. No issue for a show piece but a no go (IMP) for a working bike. Andy
A note about primerless finishes. It's well known that power paint is porous at the microscopic level and water can and will attack the steel. Wet clear coats also are well known for rusting, often at the cable stops, drop outs and the BB and headset faces. No issue for a show piece but a no go (IMP) for a working bike. Andy
__________________
AndrewRStewart
AndrewRStewart
Likes For Andrew R Stewart:
#5
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
Although actually if you are intending to file it's better to shove a bit of extra rod in and build it up a little too high.
It's not too hard to get a decent-looking stack in the actual fillets, it's down the sides that are harder because the braze is pretty much lying on top of the metal instead of having a corner to go into.
#6
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
A note about primerless finishes. It's well known that power paint is porous at the microscopic level and water can and will attack the steel. Wet clear coats also are well known for rusting, often at the cable stops, drop outs and the BB and headset faces. No issue for a show piece but a no go (IMP) for a working bike. Andy
It is a good challenge in that you really have to try and get a good finish. Paint kind of smooths things out a bit.
I'm hoping the two heat cycles isn't much of a problem but certainly I don't feel that the bronze is adding anything structurally. I've never been able to break a TIG weld in a destructive test.
#7
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,003
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4172 Post(s)
Liked 3,792 Times
in
2,271 Posts
I know, I'm not a big fan of of them. But the friend it's for is doing me the favour of letting me build him a bike so I can't argue too much.
It is a good challenge in that you really have to try and get a good finish. Paint kind of smooths things out a bit.
I'm hoping the two heat cycles isn't much of a problem but certainly I don't feel that the bronze is adding anything structurally. I've never been able to break a TIG weld in a destructive test.
It is a good challenge in that you really have to try and get a good finish. Paint kind of smooths things out a bit.
I'm hoping the two heat cycles isn't much of a problem but certainly I don't feel that the bronze is adding anything structurally. I've never been able to break a TIG weld in a destructive test.
__________________
AndrewRStewart
AndrewRStewart
#8
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
And I would be surprised if you did break a weld. But most all the cracks I've seen are from fatigue, not poor welds. Of course choosing too thin tubing and then welding with a root undercutting might be called a poor weld Still this generally needs many cycles of below max strength to fail. Andy
#9
Randomhead
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times
in
2,497 Posts
I think a first frame should have as little razzle-dazzle as possible. Leave that for the 20th frame
#10
Senior Member
Thread Starter
#11
framebuilder
Tig fillet brazing has long been an interest of mine. I used to paint John Cherry frames and he gave me some filler rod to try many years ago. I don't know what rod he gave me. We went to the very 1st titanium tig welding class together UBI offered in the early 90's. Anyway I got awesome results with a very consistent and even fillet pattern. The fillet was a bit smaller than what I usually do with a brazing torch although I liked that look just fine. The problem was that the joint had no strength. I could break the tubes apart without having to use super strength. I've never been ambitious enough to study what other kinds of filler rod could be tig brazed. However what rod I used would work just fine as a cosmetic filler over a joint already welded. Whatever I had was a low temperature melting rod.
#12
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
Tig fillet brazing has long been an interest of mine. I used to paint John Cherry frames and he gave me some filler rod to try many years ago. I don't know what rod he gave me. We went to the very 1st titanium tig welding class together UBI offered in the early 90's. Anyway I got awesome results with a very consistent and even fillet pattern. The fillet was a bit smaller than what I usually do with a brazing torch although I liked that look just fine. The problem was that the joint had no strength. I could break the tubes apart without having to use super strength. I've never been ambitious enough to study what other kinds of filler rod could be tig brazed. However what rod I used would work just fine as a cosmetic filler over a joint already welded. Whatever I had was a low temperature melting rod.
I've tried break tests on it and it is very strong. By which I mean you whale on a cromo offcut attached to something with it with a BFH and it will break eventually at about the point where the tube is fairly well buckled. But a weld cannot be broken at all. The very first test I tried was a bevelled butt joint on some 3mm flat bar. I almost bent it right back on itself before the braze material broke.
I use it on its own for bridges and bosses (although I did weld the cantilever posts) to reduce heat input and it's plenty strong enough for those. I think it would actually be fine to make a whole frame with it but it's better to weld. And I have no idea about its fatigue life.
#13
Randomhead
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,664 Times
in
2,497 Posts
testing with a hammer really means nothing in bicycle frame construction. I mean, it will tell you if you are so incompetent that you really need to take up knitting instead, but not much more. Bicycle frames fail in fatigue, that can't be tested with a hammer. Unless you are really, really patient.
It will be interesting to see your results.
It will be interesting to see your results.
#14
Senior Member
Thread Starter
Lots of good info here guys. Thank you. I've watched a couple videos of Jodi over at welding tips and tricks and he used silicone bronze. Is there a specific rod I should use? 1/16 tungsten or 3/32? What type of tungsten do you recommend?
I have experience brazing heat exchangers that I did for about a year but that was with flame and not electrode.
I have experience brazing heat exchangers that I did for about a year but that was with flame and not electrode.
#15
Senior Member
Join Date: Dec 2019
Posts: 950
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times
in
212 Posts
Lots of good info here guys. Thank you. I've watched a couple videos of Jodi over at welding tips and tricks and he used silicone bronze. Is there a specific rod I should use? 1/16 tungsten or 3/32? What type of tungsten do you recommend?
I have experience brazing heat exchangers that I did for about a year but that was with flame and not electrode.
I have experience brazing heat exchangers that I did for about a year but that was with flame and not electrode.
I use 1/16 tungsten but it's not critical. Get the 1/16 bronze rod (but for welding use a 1mm rod on most joints). I use 2% lanthanated for everything as per Jody's advice (I have an inverter machine).
Start heating the joint but don't wait for it to puddle like you would for welding, or only just. Just enough heat is when the puddle is making a nice profile at the edges rather than being convex on top. But if it is convex it's easy to just run the torch over it again to zap it in.
The idea is not to mix too much steel in with the braze. You shouldn't be melting the steel.
You can turn the gas up a bit if you like but it will always look a bit grimy when you're done. A very little wire brushing and/or scotchbrite will quickly bring back the bling.
The bits that will kick your ass are behind the seat stays and between where the chainstays join the BB shell. You will need to wrap things in foil and be creative to keep the gas where you need it. The other spot to be aware of is where the DT meets the ST. Both tubes are thin at that point so take care. Everything else on the bike is thin to thick. The top of the ST and the HT usually are thicker than the main tubes and the BB shell is really thick. So direct the heat accordingly, although this applies more to welding.
Have fun and post pictures!