I only just noticed but is that BB silver fillet brazed all the way around? How does the strength and difficulty level compare to regular brass fillet brazing?
I’ve been thinking I might want to build a “half-lugged" bike with pretty ornamental lugs at the head tube and seat cluster but perhaps silver fillet brazed BB junction because I can get custom head and seat lugs printed but a fillet brazed BB would be better and silver to keep the temps down.
Well spotted. I designed the yoke pre-mitered to match a PMW T47 BB shell and fillet brazed all the way around.
Difficulty-wise, it’s trickier compared to brass/bronze partly because of the heat-management aspect when brazing stainless, but also because the silver flows so much quicker and at lower heat.
The stuff I use is a 40% silver filler sourced locally here in Melbourne (Australia). I believe it’s similar to Cycledesign’s Fillet Pro. It builds a nice fillet if you’re careful with the heat and have the right flux. Unlike 56% silver that will just turn into a puddle.
Another bonus is that the silver is easier and quicker to finish as well.
As for strength, I can say that based on my own destructive testing when I first started using the stuff is that a steel tube will buckle before the fillet is affected.
Sounds like something to keep on the backburner until I’ve gotten a little bit comfortable with building bikes 
Although I might buy some filler in the near future to see how I get along with it anyway, I know a German supplier that has a whole list of different silver content fillers so would be interesting to compare them.
Hey @JMY,
For your final build, the single-speed setup before painting (R0002207.jpg), what did you use to replace the UDH hanger?
Could you confirm the outer thread pitch of the UDH bolt?
I have a similar idea: to make a minimal right-side insert while keeping UDH compatibility for the sliding dropouts.
I didn’t replace the hanger.
I just use a higher quality CNC-machined hanger that’s had the tab trimmed.
Ah okay, I get it now 
May I ask what tolerances you used or would recommend between the parts? I mean the tube joints and dropout assemblies. I guess it might be hard to test with an FDM printer, since the quality will be completely different from the final metal prints.
Also, I’m not sure about the threads. Do they usually print true to size, or do they need some adjustment?
From memory, I used quite tight clearances. Like 0.1 - 0.2mm
Most of the bits that needed to fit together would have been possible for me to simply file by hand if something didn’t quite fit. Luckily, everything fit nicely.
I just left anything that needed to be threaded as the nominal drill size, as if I was going to run a tap through. And during the ordering process, I specified where I wanted tapped holes. I did not print anything with an external thread.
I think the general recommendation is not to print threads.
Lots of good info in this thread:
I used .05mm clearance, and it was too tight. Next batch is .1mm, hoping it requires less hand work.
I’ve included printed threads in my models, and have confirmed the thread size and pitch with Protosoon. Not sure if they print the threads then tap, or if they print straight and tap.
I go a full 0.1 gap all round so 0.2 undersize of diameter and is usually good. Threads will either be tapped or machined if big enough ie. I had them cnc the T47 threads in the last shell I had printed