My first brazed joint #1...

[beardydave]

So... Having spent the last three weeks scouring the salon for inspiration and advice, i finally bit the bullet and wielded file and torch in anger for the first time! My hands are still shaking...
I was kind of hoping for a perfect fillet braze to drop out of the end of the torch, but funnily enough I ended up with this:

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Too hot I assume?

Thankfully i have lots more practice parts to destroy before frame #001 gets so far as the scale drawing!

[steve garro]

IMG_4551.JPGDon't take this the wrong way, but you have zero heat control.
Get a flat piece of plate & try to do a line of dimes of try to stack brass globs in a tower without melting it down - may I also suggest building something nonstructural before a bicycle.
- Garro.

[beardydave]

Thanks Steve!

I'm well aware that it's awful (it is quite literally the first time I've brazed anything), and trust me I won't be pointing a torch at anything other than the big pile of practice bits I've got here until things look considerably closer to your picture than mine!

It seemed to get that hot incredibly quickly... should I be using a smaller nozzle than nr 5, or a cooler flame?
Not that I'm looking for excuses of course. Probably.

[steve garro]

Thanks Steve!


It seemed to get that hot incredibly quickly... should I be using a smaller nozzle than nr 5, or a cooler flame?

Oh, geez - I fillet with a #1 Victor.
- Garro.

[MacLaughlin]

... i finally bit the bullet and wielded file and torch in anger for the first time! My hands are still shaking...

Fury is okay, but anger might be a bit much; You can't dance angry.

[Clockwork]

Use a smaller neutral flame and get it really close to the work. Rotate your wrist to move the flame completely off the work for a second after you lay down new brass.

-Joel

[beardydave]

Ah ha! I'll try a #1 next time then. No doubt it will be flawless :-s

You can say what you want about my brazing - just leave my dancing out of it

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[dbohemian]

Get a flat piece of plate & try to do a line of dimes of try to stack brass globs in a tower without melting it down - Garro.

Agreed 100%. Worth a shot to see what would happen but you need to start out on some simple flat plate and just get used to melting some metal. Work with a #1 or #2. Neutral to ever so slightly oxidizing flame and just look for the change in your flux (shiney) that indicated the metal is receptive to the bronze. Castle building is a great excersise. Don't try and stick anything together yet. Take picture report back. It will take me about a month I think but I was going to make a fillet brazing vid for all the world to see. A little video is worth a thousand words.

Here was some stupid thick assed tube wall practice brazing I did the other day cause I am working on a future motorcycle project.



Honestly, you can do this in relatively short order. Ignore the lack of flux...using gas fluxer, I recommend paste though as Steve shows.

[Andrew R Stewart]

+1 on the recommendation to play with brass forms, towers, bead lines. Consider not adding brass to your steel but just heating it with flux to see only one thing at a time (in this case it would be the color of the steel and the look of the flux). Try placing a ring of brass inside the tube that butts up to the other one. Heat and see if you can get the inside ring to melt out.

I find the size of the tip and how close it is to the joint controls how fast and how high the heat gets. Flicking the flame away (to a side where the flame won't hit something else) and then back onto the joint will control the heat level's consistancy. Beginners usually find it easirer to keep a handle on the various factors if they use small tips.

One way to braze a tube joint is to do the flowing (sometimes called the wetting out pass) first then go back and start to build up a fillit bead. The first flowing step uses a broader flame/heat focus and the fillet uses a smaller flame focus.

Can you get to watch some one experienced? As Doug Fattic says it's easier to learn good techniques first then to unlearn bad ones later. Andy.

[false_aesthetic]

I'm learning more from this thread than I did in my foundry class in undergrad.

Of course, all I needed to do back then was stick a bronze sculpture on a piece of steel and have it last through a 4-hour critique.

I'd love to see the video when it gets made.

[beardydave]

Thanks a lot for all this guys - I've got a couple of bikes to service and a rugby game to watch later but hopefully I'll fit some practice in.

As Doug Fattic says it's easier to learn good techniques first then to unlearn bad ones later

I totally agree but regrettably I don't know anyone with the skills to share! I'd love to spend a bit of cash on a course but spare cash isn't something I'm currently over-burdened with - maybe later in the year.

I'll report back later when I've cooked some more brass!

[beardydave]

Hi Guys

Not had chance to get back to the workshop yet, but I'll be there tomorrow.
I'm still not 100% clear on what's meant to be happening at the business end of things (ie is the bronze being melted by the heat from the steel or direct from the flame?) so I was doing a bit of you-tube research. There's surprisingly little that shows what's actually happening where the braze is formed. This is pretty much the best I could find:


Clicky linky

Would you say that first 2 minutes is a pretty good example of what I'm aiming for?

[Clockwork]

That's welding. The brass is melted by the flame and the base metal should just be at a temp. that it accepts the molten brass. When you see your previous brass addition melt and creep into the joint seam, then add more brass.

[steve garro]

Hi Guys

I'm still not 100% clear on what's meant to be happening at the business end of things

It's good to understand the physics of what you are trying to do........
Brazing - Wikipedia, the free encyclopedia
- Garro.

[dbohemian]

That's welding. The brass is melted by the flame and the base metal should just be at a temp. that it accepts the molten brass. When you see your previous brass addition melt and creep into the joint seam, then add more brass.

The beginning of the video was welding, he moved into brazing later but he was much better at the welding so ignore his brazing technique. Just want to clarify. The filler metal is melted by the base metal, not in particular the flame. Small difference, can seem the same but sometimes a Padawan will just glob the filler on the steel because it is still too cold but they can melt metal with the flame. BeardyDave, nothing beats just melting a bunch of metal. People practice far too little and expect a lot. Just heat the steel and melt some metal on it to get a feel. Or wait a month or so to see that video I plan to do. I would recommend messing up some steel though. :)

[boxerboxer]

How similar is it to soldering, if you ignore the difference in the way heat is applied?

[dbohemian]

How similar is it to soldering, if you ignore the difference in the way heat is applied?

Conceptually, especially with lug brazing it is very similar. You want to bring up the entire brazing area to exactly the right temp and the filler metal will flow throughout the joint. Industrially they do this with ovens or induction coils that bring the part to a very even heat and then the brazing only takes seconds. Fillet brazing is a bit different but not a lot, just more pinpoint and precise. The idea that we are just constraining the weld bead to a small area, not a whole part and therefore it can seem like we are melting the rod with the torch but the base metal must be at the proper brazing temp for everything to work correctly.

[Mark Kelly]

How similar is it to soldering, if you ignore the difference in the way heat is applied?

I agree with Dave above but from the opposite viewpoint: after 30 odd years experience with soldering electronics I recently had to braze a lugged bike frame.

I read all the advice here then ignored most of it and jumped straight in the deep end. I think the soldering helped me understand what the metals were doing; in both the primary aim is to avoid cold joints, it just takes bit longer to get to temperature when brazing.

[boxerboxer]

Thanks, Dave and Mark. Hopefully this will help that first joint come together just a little better when I finally get around to it.

Ben

[beardydave]

Had a go at laying some beads down. struggling wirh uploading photosdue to a downgrade of phone so I'm afraid a Flickr link will have to do! 2 photos, practice brazes numbered in order!

practice 2 | Flickr - Photo Sharing!
Struggled getting the neat stacks of coins - I think I'm still heating the steel too much...