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Discussion Starter · #1 ·
So I am a frame builder. I am planning a commuter bike for the wife. It will not be ridden hard or off road. To be different, I was thinking of building a frame from T304 stainless steel tubing (the generic stuff not reynolds 953). I was going to use stainless drops and a stainless unlugged BB shell from NOVA. Instead of using lugs, I was going to just braze (not fillet brazing because I won't be building fillets) with 45% silver brazing rods. I was going to put into some redundant supports to compensate for this relatively weak joining plan. Anyone know if I can use 15% silver on stainless instead of 45% or 56%. Anyone else have anyother advice.

Marc CHimonas

Fort Collins CO
 

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Silver fillets = scary

If I were doing this project (which I think is a neat one) I'd either TIG the frame, build with appropriate stainless lugs (there are plenty to choose from), or else make some lugs with the lathe and tig them together (if the commercially available lugs aren't appropriate), then silver braze in the main tubes. Any of those solutions would work well, I think.

I know there are a couple of people who have done silver fillet brazing in the past (and possibly present). Jalon Hawke is a name that comes to mind. But I also know that unless you're a *master* at the technique, it is super dangerous - the fillets can crack very easily as they cool, as the silver changes volume quite a lot when changing state. I don't think redundant supports (other than lugs) will be enough to hold this together.

But then again, I am not the fillet expert. See if you can find some info on the framebuilders/phred archive. I know this kind of thing has been discussed.

-Walt

mchimonas said:
So I am a frame builder. I am planning a commuter bike for the wife. It will not be ridden hard or off road. To be different, I was thinking of building a frame from T304 stainless steel tubing (the generic stuff not reynolds 953). I was going to use stainless drops and a stainless unlugged BB shell from NOVA. Instead of using lugs, I was going to just braze (not fillet brazing because I won't be building fillets) with 45% silver brazing rods. I was going to put into some redundant supports to compensate for this relatively weak joining plan. Anyone know if I can use 15% silver on stainless instead of 45% or 56%. Anyone else have anyother advice.

Marc CHimonas

Fort Collins CO
 

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Discussion Starter · #3 ·
So I wasn't actually going to build a fillet. By fillet I mean that ring of filler that goes around the actual join that makes the join look seamless. Rather I was joint going to fill the join itself (old school brazing no fillet). I don';t have access to a TIG welder (or a mig welder for that matter). I read that at brazing temperatures stainless steel tubes can loose thier stainless steel properties pretty quickly so there is a need to be fast. Lugs would be a bit problematic because you cannot see what goes on undernieght the lug, the conductivity of chromium means that I would probably need higher heat to get the silver to flow where I want it to so I may over heat the tube ends and lugs. THe purpose of the redundant supports would really be just to stiffen the frame so that there are less sharing forces of the joins.
 

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Ummm...

I think you need to rethink this. It sounds to me like you might need a lot more practice before you do anything with stainless steel.

What do you mean by "fill the join(t) itself"? Fill what? The inside of the tubes?

My best advice is to get some stainless tubing that will slip fit together (make it on a lathe as needed or find the right ID/OD) and practice brazing it together until you can get good penetration through the "lug". Then buy some stainless lugs and build this thing.

Stainless tubing and lugs are used all the time for framebuilding. It's a versatile and safe method of joining tubes, and you can build a great bike with it. Don't try to cut corners and make something unsafe because you didn't want to invest the time to do it right.

-Walt

mchimonas said:
So I wasn't actually going to build a fillet. By fillet I mean that ring of filler that goes around the actual join that makes the join look seamless. Rather I was joint going to fill the join itself (old school brazing no fillet). I don';t have access to a TIG welder (or a mig welder for that matter). I read that at brazing temperatures stainless steel tubes can loose thier stainless steel properties pretty quickly so there is a need to be fast. Lugs would be a bit problematic because you cannot see what goes on undernieght the lug, the conductivity of chromium means that I would probably need higher heat to get the silver to flow where I want it to so I may over heat the tube ends and lugs. THe purpose of the redundant supports would really be just to stiffen the frame so that there are less sharing forces of the joins.
 

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Discussion Starter · #5 ·
This is what I have in mind (only not so fancy: http://desperadocycles.com/). Here, the builder has a fillet brazed reynolds 953 frame using 45% silver. He admits the fillet is really ornamental and doesn't add much to the strength of the join.

In frame building, builders often think of only two types of brazing: fillet brazing and lugged brazing. Outside the world of frame building, fillet brazing is called braze welding. YOu braze the two pieces of steel together then you weld brass onto inself to reinforce the join. Outside frame building, brazers often braze without building up a fillet. Basically you get a small ring of filler to connect the two peices of steel together but you don't build up the fillet (a larger ring to reinforce the join). I've got plenty of experience in silver brazing, and have used this method for smaller parts such as stiffeners. I can't find lugs that will give me the geometry I desire. (Also, I am tired of making lugged frames). The bike will not be ridden off road or hard. Basically it's a cruiser. Is there another type of filler that works on stainless other than brass?
 

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Yes, I call it an internal fillet. There was many ways it was done. There have been many older frames and even the famous Schwinn varsity had a joint or two done this way.

Does it work? yes, of course. Does it work well? no. Mostly as you said, only for light use structures. I have seen this type of construction fail catastrophically twice up close in my life. Not something I can recommend.

Personally I think the whole idea is kind of flawed. I have thought it out myself over the years but 304 is really not a great or even good material for building frames for all sorts of reasons (reason #1 is that its about as strong as a frozen stick of butter). By the time you make a suitable internal type lug/reinforcement situation you will have a ton of time in it and it will be experimental.

Silver fillets are possible. Freddie parr has a good material called fillet pro I have built stuff out of. It costs a ton. I don't know what is in it. There is also allstate 11 which I have used too but its a very high temp material and distorts the crap out of 304.

I would recommend building a cool frame out of 4130 with bronze and have it electroless nickel plated if you are looking for corrosion resistance.

I try to remember that trying stuff out of the ordinary is cool but faceplanting when you frame separates into multiple pieces is not. Better to play it safe.

Dave Bohm
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Discussion Starter · #7 ·
Ok... I guess what I am trying to get at is to ask if practicing on t304 would have any value for one day working with Reynolds 953. I've had plenty of practice on Cromoly but I keep reading how difficult stainless is to work with?
 

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mchimonas said:
So I wasn't actually going to build a fillet. By fillet I mean that ring of filler that goes around the actual join that makes the join look seamless. Rather I was joint going to fill the join itself (old school brazing no fillet). I don';t have access to a TIG welder (or a mig welder for that matter). I read that at brazing temperatures stainless steel tubes can loose thier stainless steel properties pretty quickly so there is a need to be fast. Lugs would be a bit problematic because you cannot see what goes on undernieght the lug, the conductivity of chromium means that I would probably need higher heat to get the silver to flow where I want it to so I may over heat the tube ends and lugs. THe purpose of the redundant supports would really be just to stiffen the frame so that there are less sharing forces of the joins.
cool! build it, let's see what you come up with! :D :thumbsup: :cool: :) ;) steve.
 

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Discussion Starter · #9 ·
OK... after much pontificating I changed my approach a bit. I decided to buy thickish (1.5mm wall thickness) straight guage T304 tubing for the seat stays, down tube, seat tube, and down tube. Everything else will be regular cromoly. I will used lugged frame constuction instead of fillet brazing or internal brazing. THe bike frame will be heavy. Anyone have any additional comments or feedback.
 

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Why are you so resistant to everyone's suggestions? From the posts you've made it sounds like brazing and framebuilding in general is new to you. Stainless is not like working with other metals. Do you want a shiny frame then get it nickel-plated as suggested. If it's corrosion resistance don't worry about and Framesaver the inside of the tubes. 1.5 is really thick and the ride ride isn't going to be that nice unless your design makes up for the ride differences of thick tubing.

I'm all about DIY, but if you're going to do it do it right.
 
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