Stack of dimes brazing technique
 

I recently watched this interesting youtube video on fillet brazing technique for fabrication of a motorcycle frame;

His technique was to produce brazed joints that look a lot more like a TIG weld "stack of dimes" rather than smooth fillets Ive always seen used on bike frames. I would be curious get opinion on this brazing technique from some of you more knowledgeable framebuilders (DOUG!).
The guy in the video suggest that these "dime" joints are easier for him to produce than using smooth fillets. Might be that his technique is better suited to joining thicker moto frame tubes, not so applicable to thin bikes?

The stack of dimes technique works on bike frames, brompton uses it. I suspect it's easier once you learn to do it. There is a lot less finesse involved. Heat, fill, pause, heat, fill and repeat. All muscle memory.

He's doing a very nice job. Interesting that he hasn't put any flux on the joints but is just relying on the inline fluxer. He also has quite a big gap in his fit-up at the other end of that tube he's brazing in the first part of the video but it doesn't seem to be a huge problem.

I made this its own thread because I thought it was interesting and didn't want to derail Andy's thread.

I thought it was interesting that the gap on the other side of the tube opens quite a bit as he starts brazing. I imagine it closes again as the frame cools.
Or maybe not.

I'm going to try it and post some pictures here. It would be great if other people did that too.

I saw this video surfing YouTube videos. I'm not a fan of the way stack of dimes fillet brazing looks but I don't hate it either. I see it as a method to produce an acceptively attractive joint without any need for after brazing filing. In other words the advantage of this method is the time it saves and not how beautiful it looks. Perfect for a pro wanting to reduce his build time.

I don't see it as a method for part time or hobby builders either that can take more time refining each joint. Andy's MTB is a good example. His flllet brazing was okay and he did it twice to refine his 1st attempt. However he could file his joints beautifully. I doubt most amateurs want to spend the practice it would take them to achieve acceptable results when they can file after brazing to make it even more attractive. And I can also say there is a certain percentage of brazers that would have trouble ever making stack of dimes look decent no matter how much they practice.

Well, my motto is "No file" so it's perfect for me.

I think it looks good, I actually don't think I would make any bikes that way though. The fact that it can be a little irregular and still look okay is good for the motorcycle builders, think about filing all those joints, it would make me cry.

That's perhaps a bit harsh :) If I could stack brass dimes like that guy I would be proud of it and want to show it off. Which is more beautiful? Well it's subjective but I'm always impressed by a joint that didn't need any cleanup.

People used to quite often file TIG welds smooth but that's considered cheating these days and everyone wants those dimes. But whenever I'm swooning over dimes my wife and other normal people say what they're actually pretty ugly and they're right. They only look good because you know they're hard to do. To the "untrained" eye they look like maggots curled up around the joints, which most people hardly look at anyway.

The biggest priority, especially for a hobby builder, is strong and sound joints, closely followed by good alignment. Filing after brazing is not that easy either! I TIG everything but I did make a frame with TIG braze over the welds filed smooth to get that look. It was OK but nothing like what Andy's looks like.

I noticed that as well but wasn't sure if i was seeing what I thought I should see or if it was really opening. You can also hear 'pings' as the tubing heats and cools.

I'm with Doug on this . This technique seems like a good way to streamline the process - one brazing op - rather than brazing, soaking, rough filing, sanding and polishing. Each of those ops potentially have a different tool and it's own muscle memory. It also enables a builder to differentiate and build a story around their technique and resulting frame and target people who appreciate this joint type while also being profitable and ensuring they're in business for the long haul. Curtis BMX frames in the UK uses this technique. I think it has a certain purposeful beauty to it but the flow of a really nicely done smooth fillet braze is my preference.

I did try it on my current project. I think using a bigger rod and thicker tubing might help with the 'dimes' definition. In this picture you can see faint ridges. This is with O/A, victor #1 tip and 3/16 rod and 0.8mm DT to 1.0mm HT. I think just watching that video and then mimicking the motion and rhythm is good practice for developing the muscle memory. All other high performance pursuits utilize visualization so, no reason brazing wouldn't do the same. My wife thought I might be having a stroke at the dinner table as i used my knife and fork as a torch and filler rod.
https://live.staticflickr.com/65535/...7baa4a29_b.jpgUntitled by Duane Draper, on Flickr

Looks nice. I think you're right about using bigger rod. Also it seems like some people pull the puddle towards the un-brazed tube a little

If you don't use any flux (apart from the inline fluxer) does it make the dimes "stick" more instead of flowing and losing definition?

I don't think flux has anything to do with it, but people that use this technique tend to have gas fluxers.

Isn't the flux supposed to help the filler metal flow better though? If you solder copper plumbing joints the principle is that the solder goes wherever you've put flux. This may be why duanedr's "stack" is so much flatter and more wetted in. It is a very nice looking joint and probably stronger but this may explain why it doesn't have the same bead profile.

There is flux in a gas fluxer?

Yes but it's not spread all over the metal. This article is quite good:

https://www.harrisproductsgroup.com/...ing-works.aspx

The filler metal is being pulled in two directions at once. It wants to make itself into a little blob but it also wants to get sucked into the parent metal. A stack of dimes is a fine balance between the two. If you cover the parent metal with flux it may make the "adhesive" force stronger compared to the "cohesive" one. The best way to find out would be to try it but I don't have a gas torch with or without an inline fluxer.

Gas Fluxer- I used one (actually one of two different brands) for a few decades before I retired the last one about 15 years ago. Sold it last year. Flux does nothing to change why the filler wets out but everything to do with keeping the base metal oxide free so how the filler wets will work as intended. I found that using the fluxer only made for frustrating brazing as the base metal could more easily become carbon coated (or whatever the black stuff is) or a too hot spot would burn more quickly. Paste flux only works, as most here already know, quite well. Both together seemed to extend the flux's "life" and slightly reduced the amount of blackening or burning, but only slightly less. Clean up with both is about the same as paste only, maybe slightly nicer as the bad spots might be lessened.

But to repeat it's my understanding that the flux, whichever method is used, only keeps the metal clean to accept whatever filler is being used. It's the filler/base metal and skill with the flame that determines who nicely the brazing ends up. Andy

I don't think so. I think it's more that the timing (letting the puddle freeze and joint to cool slightly) and building up enough mass with the prior puddle that it doesn't re-melt when laying the next one. When H-J was clearing out, i bought filler and they threw in what feels like 1/4" filler rod (probably 1/8th but, man it feels chunky). With the fatter rod, it's more important to keep the rod tip 'in the flame' so it stays near melting when it's not actively being dipped. Having said that, I would love an inline fluxer but just don't think the mess/storage/cost etc. is worth it at this time.