You can’t use too much flux - especially if it’s going on IG! 
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Hey… Thanks @Duanedr
Yeah… Need to cut that piece in half. Will do that. Makes sense for a more uniform distance between the tubes…
Hmmm… Tried the more distance and less heat thing. But the 45 wasn’t melting. I’ve not tried 55. But I think I understand when you say the 45 doesn’t flow.
Which leads to the next question… Was the heat on the steel tube - judging by the colour of the hot tube - in the right ballpark? (light red)
Or was it too much?
Coming to your next point, yes, I’ve got bronze and the specific flux needed for it. Will try that next (with a bigger flame.)
So if that works, does that automatically mean 55 should also work under similar conditions?
Or more importantly, can I then bronze solder (for want of a better term) the steering tube to the fork crown?
@project12 charged as guilty. Will add more flux. What can I do? I am a big Brodie fan 
Also will heat it up from the inside and try a few times before trying bronze.
I am doing all of my silverbrazing with 45% and in my experience this should work pretty too in your case. And Brodie is awesome, you can copy him when you have the same years of experience. 
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So folks have mentioned most of what I saw but here’s a few other things:
- I prefer to bring the entire circumference of the joint close to brazing temperature before I start adding filler. This way 1 part of the joint isn’t wicking heat away from the area you’re trying to braze. It also means that you’ll have a better ability to pull the filler in/around the joint without over-cooking the tube.
- Silver flux, IIRC, is active in the 550-850C range and 45% silver has a brazing range of something like 750-850*C (my memory is fuzzy. You should confirm with the data sheets for your specific material). How does that match with the color chart I’m posting below? My guess is that the areas that heat up to red are a bit hotter than the flux can handle and that’s why you’re seeing the charring on the outside. And, if there’s charring on the outside, then there’s charring in the gaps. Filler (LFB or silver) doesn’t like to flow into charred/dirty areas.
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Lots of helpful suggestions so far. I noticed a couple moments in the video when the smaller piece was too hot and the tube had no color. Also, the filler at the edge of the cooled joint had a lumpy texture, indicating the joint was not heated evenly enough inside to wet out and draw in the filler. You need both pieces to be up to temperature in order to get the capillary pull. As @project12 says, spend some time heating the inside of the tube. You will need to do this when brazing a crown to a steerer tube.
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Woah… This is super helpful guys! @ElysianBikeCo @scharencycles
Danke! 
Can’t wait to get back to my cave, & implement all of what you wonderful ppl have highlighted:
- Get a consistent gap between the 2 parts
- Add More Flux - inside and outside!!!
- Heat the inner part and bring it up to temperature.
- Then get the circumference of both parts upto temp. (Dark dull red metal or untill all flux turns watery.)
- Keep the temperature to a lower shade of red. Don’t get the flux charred.
Will update soon. Thanks
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And once you burn the flux just stop, clean everything and start over.
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Once it goes to red, you’re at risk of cooking the flux. Having a gap between the layers doesn’t allow the heat transfer to the inner tube so then you’re cooking the flux between layers and then the silver won’t flow at all. 45% is just ‘gummier’ than 56% which is why most use 56% for lugs/lap joints like you’re doing. 45% will work for fillets but not lugs.
56% and brass are very different. Brass/Bronze flows at a higher temp and at the higher temp it flows better into a gap than 45% in my experience.
You’ll want a bigger gap for brass - like .009" or 0.25mm. The outer piece should easily slip over the inner tube. You’ll want .004" or 0.1mm for 56% silver and there is likely some friction between the two pieces.
To be honest, I have only tried flowing 45% like you’re doing once or twice (and one was by mistake!). I just know it’s more challenging so I stay away from it for lugs. Cycle Design has their System 46 that actually flows very nicely but I don’t know the make-up of that vs 45% or 56%.
For lugs and big lap joints like you’re doing here, I use the largest Paige Tools tip and Oxy/Propane and I try to get a big soft flame and then hold the torch back just a bit so the heat isn’t quite so localized.
Bronze/brass is fine for crowns, you’ll just want the bigger gap.
Keep at it!
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Something I found that helped me not overheat the part was to flick the torch away often. Just for a moment.
Good luck! If I could figure it out you will too!
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Hey Guys…
Took all of your advice and gave it a try again.
Lots of flux, internal and external heating etc.
The flux really helped… @project12 thanks
It gave me a bigger window before frying stuff… Even then, the flux got fried in the 1st attempt
But the 2nd and 3rd attempt weren’t so bad… Less burnt flux and good coverage. Probably I over heated the inside part as there is no line of sight. But it’s better than no heat at all.
The silver hasn’t come out from the other end yet… But there is good coverage (I cut it open to check.)
Will keep trying…
@Duanedr didn’t try with bronze yet… But will give it a shot after I figure this out. Bronze solder sounds pretty interesting .Thanks for the gap profile info.
@Johnmarmalade Thanks for the encouragement. Trying the flicking game. Will learn someday
Shot a video and a few pics… But can’t upload the video from my phone for some reason… Will try from the system soon.
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Feedback from your video:
-pre-heating everything way too much, so when you get in there with the torch the entire workpiece is already hot and you only have a couple seconds (literally) of working time before it overheats/burns.
-too much time with torch on the workpiece, generally in brazing and especially with silver, you should be backing the torch away every 2-3 seconds for about 1-2 seconds. Brazing temperature is a small window from liquid to boiling/burning, and your goal is to keep the temp essentially just above liquid but well below burning, but with a torch that is much hotter than your working temps - so you have to remove the heat input frequently to not overheat.
-workpiece is too hot and flux is burning before you are even getting on the edge with your silver. Silver is also very sensitive to contamination, and it won’t flow/stick to where any burn is, so if the inside of that joint is burned, it won’t flow through at all regardless of how much you do with the torch. That’s why it’s all stuck in a lump on your edge there.
-hard to tell exactly from the video but based on what’s happening with the flux, your torch is still too hot or is oxidizing flame. Try a smaller overall cone and make sure you are not oxidizing - slightly carburizing/reducing flame (tiny bit of a shadow around the cone) is preferred for silver. If your torch is oxidizing at all, everything is going to burn crispy black before you can get any filler in.
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moving around too much. If your goal is to get filler to flow from the top to bottom of the piece, you have to slowly give the filler a pathway with heat. Even if the distance is only say 1” total, you can’t jump from top to bottom of that distance with the torch and flow it through - there’s probably a cold spot in the middle somewhere. Break it down into 4 smaller sections no more than 1/4” at a time. Pull filler from top edge to just a 1/4” bellow edge, back off for a sec. Then go from the bottom of that section down again 1/4”, back off to cool. Repeat again until you make it to the bottom of your piece/joint/lug.
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for your practice pieces drill some holes about halfway through the piece from the top. This can give you a visual if the silver is flowing at all. If you are adding from the top edge and silver is wetting out the drill hole, you’re at least getting it to that depth on the workpiece.
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Also some folks have referenced the working temps and the heat chart which is great to keep track of, but a good visual rule of thumb for silver is that if you’re getting any colour on the metal (seeing any red at all) it’s too hot. You should be below red base temp on the workpiece at all times.
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Thanks for these… Understanding the pattern helps to learn the dance!
This makes things clear!
Thanks Danielle for your inputs. (As also all the folks above.) These should work as markers on an uncharted road (cairns). Was getting a bit frustrated at the lack of results. Will try again by working on rectifying these issues.
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