Yet another fillet brazing question

[Nic]

Sorry to weary those who answer these queries ad infinitum but would just welcome views on the problem. Have read through all the advice on this and other forums and practised over and over, and hit a bit of a wall, compounded by ignorance. Boiled down it is this -1. if I tin the joint and then do the fillet in a second pass I produce neater work with a good internal fillet but the joint is kept heated for much longer - around 8 to 10 minutes, including pre-heat of joint (about 1 minute 30-2 minutes)

or
2. I go with higher heat, in one pass and get it done quicker (not in Garro or Estlund time but quick for me -5/6 minutes) trade of being the internal fillet is rather haphazard and generally covers about 70% percent of the circumference.

It seems from what I have read fairly evenly divided between those who tin and those who don't and I am aware that personal choice probably dictates a great deal of this, but from the point of further practice I would welcome opinions on whether I should concentrate on one or other method. Would like to post pics but in the absence of my tech savy son can't work out how to do this

Nic Whitwell
Suffolk
UK

[Eric Estlund]

Both methods are all about heat control and managing your time. I spend more time preheating than I do filleting. Really, they are the same technique as far as the brazing goes- it's just how and where time is divided. When I tin it's generally for reasons other than building an internal fillet. If your one shot isn't doing it, it's because you are rushing. Pushing a tin is a full heat deal if you are sucking it in. I just use that time to also lay the meat.

[e.Gellie]

Practice more. I suggest you set up to do 20 practice joints, especially if you have no-one there to instruct you as you braze. You will improve, get faster. If you use short sections of tube mitred for a T-joint, you should be able to look down the tube to check the penetration as you work. Preheat of the whole joint is essential.

[Eric Estlund]

Short sections will preheat faster than full length tubes, but that is great advice to get the ball rolling. Heat control is all about timing and intuition, and that intuition is the result of experience and practice.

[Nic]

Thank you very much for the advice and suggestions -very much appreciated.Eric it was very helpful to think in terms of it as a single process. Ewen -thanks I think I will do just that, have been doing a bit every few days, will settle down and prep for a fillet fest. It will do my filing skills good as well!

[Doug Fattic]

What I recommend for practice is fillet brazing a short piece onto a long piece. The long piece can be used as a convenient handle to keep your joint in the right position as you go around. That ability to keep the joint in the correct position (so the brass isn’t more likely to flow to one side) is one of the key elements for success just like heat control.

Furthermore it makes sense to start out with a bigger diameter long tube (maybe 1 1/4” in Ø). The short pieces can be smaller in diameter (maybe 1”). This also works out well for conservation of tubes because the used end can be cut off for a fresh start without much waste. Eventually as mastery is obtained the short pieces can increase in diameter.

Most likely the practice tubes will be .035” (about .9mm) in wall thickness but again as one catches on the long tube can increase in wall thickness to imitate a heavier head tube so the flame adjustment required for this type of joint can be practiced.

It is self serving to say this but those that want to be really good will somehow get lessons from a master. This not only really shortens the learning curve but also shows the methods that produce the best results right from the start. Rookies all make similar mistakes and self instruction doesn’t get one out of those ruts quickly.

[Burcak Erbil]

To my knowledge (as a Metallurgical engineer) the timeframe that really counts is when the steel is heated above 700C or so (When it starts to glow red) That means for fillet brazing only the point you're working on is affected. Tinning+brazing increases this time considerably of course as each point is subjected to this elevated heat twice.

Beside time, the width of the heat affected zone is another point. As I have seen there are two distinct fillet brazing methods; one that's mostly used by British (penny-stack looks) and the other mostly used by the Americans (smooth looking). I have learned the British way. As far as I know the heat used is lesser and more concentrated on the British method, but could not really compare how much as I don't know the American.

Having said all that, I do not really concentrate on the time, I try to focus on applying the correct technique and when it works smoothly and nicely, it turns out reasonably quick too.

I could not emphasize the importance of a proper course if you want do this seriously.

[Nic]

Thank you very much Doug and Burcak.
I have adapted my practice following your advice Doug and it is much quicker to set. Thank you Burcak for the metallurgical input; it conforms what I have found from other sources. I assume that the method you us, I am guessing it is the Brian Curtis/Bicycle Academy method uses a single pass? I think that I will attempt to try to practice a single pas. I just find it rather hard to see what is going on when using a single pass.

[Eric Estlund]

Nic- the "seeing" comes from practice. It is certainly in part actually using your eyes, but it's also having the experience to anticipate what is happening and what is about to happen. I've laid some pretty killer fillets without really "looking" (that is, visually focusing on and cognitively processing) the work because I have the torch time to anticipate the reaction to my inputs (fire/ filler).

[steve garro]

I've laid some pretty killer fillets without really "looking" .

So much of the time I'm not able to see the puddle at all, as I'm in my wheelchair brazing - I'm brazing "over the hill" but I know where the puddles go.


- Garro.

[Burcak Erbil]

Thank you very much Doug and Burcak.
I have adapted my practice following your advice Doug and it is much quicker to set. Thank you Burcak for the metallurgical input; it conforms what I have found from other sources. I assume that the method you us, I am guessing it is the Brian Curtis/Bicycle Academy method uses a single pass? I think that I will attempt to try to practice a single pas. I just find it rather hard to see what is going on when using a single pass.

Yes, I've learned in TBA.
I agree with Eric. I do not really see the fillets I'm laying simultaneously. What I want to see is the wetting of brass in the root and to the sides of the fillet, forming the desired radius. Then the resulting brazing turns out good.

[waterlaz]

Not to multiply threads I'll just ask here.
I've done some amount of fillet brazing with CuZn rods from the community store (1kg of fillets). Now I got the GasFlux C-04 brass rods and I absolutely hate it.
And I hate it for the reasons that are usually listed as benefits. With the older rods the brass got very liquid very fast and I could easily control the form of the puddle. With GasFlux it takes annoyingly long time to go from liquid to solid.
I still can make fillets that I am at least somewhat pleased with but it takes me roughly twice as much time.
What may I be doing wrong? Should I stay at lower temperatures?

[Eric Estlund]

CuZn (that is, RBCuZn-C) and C-O4 (RBCuZn-B) only have a 10*F difference in melting point. I'd suggest your torch settings and general pre-heat are off (probably for both).

[Doug Fattic]

Evgeniy, when you visited our bike/frame shop on our college campus in Bucha, the bronze rod I gave you to practice doing a fillet joint was Gasflux’s C-04. I remember you did really well with it. Perhaps you got used to the characteristics of the rod you bought in Ukraine with lots of practice and found the changes to C-04 less to your liking rather than more? Most of my frame building students have trouble controlling the temperature right at the melting point of the brass (actually bronze but western frame builders call it brass) when they are first starting out so something that allows them a bit more time to recognize the heat indicators so it doesn’t run away from them is an advantage. So I am a bit mystified if the problem is just a preference to something you have gotten familiar with or in your torch settings. It is possible your skill allows you to react faster so the brass doesn’t run away too far like what happens when the heat is kept on the joint for just a nano second too long. That is typically what happens when my students are beginning.

In other news I see there are 2 bike shows in Kiev this spring. One at the end of February and the other in March. Can you find out a bit more which might be the one either Tim or I need to attend to get some of our parts for our transportation bicycles at wholesale? I think you have indicated that at least one of these shows is basically a retail consumer show. My friend Tim went to the Polish show a couple of months ago and found some suppliers for us like the rear racks made in that country.

[waterlaz]

Eric, Doug, thank you. I think I'm getting better with the new rods.

In other news I see there are 2 bike shows in Kiev this spring. One at the end of February and the other in March. Can you find out a bit more which might be the one either Tim or I need to attend to get some of our parts for our transportation bicycles at wholesale? I think you have indicated that at least one of these shows is basically a retail consumer show. My friend Tim went to the Polish show a couple of months ago and found some suppliers for us like the rear racks made in that country.

I'll find out.