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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 06-30-09, 06:08 PM   #1
hammer11
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Brazing a lug help

Hey builders, I was hoping to get a few tips on brass brazing lugs.

I can silver braze lugs no prob, brass is proving hard for me to do clean work with.

It seems that no matter what method I try I make more of a mess than I would like. There is always some spillage over the lug and always some charred flux which has proven very difficult to remove with a soak and even wire wheel.

I am using Harris paste flux. I am mainly using a small and strong carburizing flame Victor tip #2. I have tried putting no flux on the outside of the lug which seems to keep the spillover to a minimum, but the problem is the lug gets oxidized.

Is getting no spillover just asking too much?

Are there better fluxes to use?

Should I cover the outside of the lug with flux, or should I leave it bare?

Thanks for any tips.
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Old 06-30-09, 06:48 PM   #2
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I don't build lugged frames only fillet-brazed but I was taught that silver brazing is the preferred method for lugged frames. The tolerances are supposed to be pretty tight and the brass won't flow as freely as silver. With that said, I know that some builders do use brass with lugs. As far as flux goes I haven't used Harris flux but I would imagine you always need to flux your joints to prevent contamination. If you are pretty good with the silver brazing why not stick with what works, the temps needed are much lower and less stressful on the tubes. Good luck.

Dimitri
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Old 06-30-09, 09:02 PM   #3
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Thanks for the input.

I have my reasons for doing brass... Anybody with brass lug brazing experience who can answer my questions?
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Old 07-01-09, 07:29 AM   #4
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I am not a huge fan of the Harris black flux. You are using the black and not the white, correct? I have found greater success, cleaner shorelines, and easier cleanup using the Gasflux blue Type "B" paste. You can get it from Henry James by the one pound tub. You might also want to get a pound of the c-04 1/6" rod and see if that doesn't help as well.

To keep the bronze from spilling over onto the lug, try to heat from the inside out. Heat the outiside of the lug just to keep the flux in place.

Full disclosure, I use silver predominantly for lug and bronze for fillet brazing but there are many many many frames out there that used bronze as the filler metal. If you can lug braze with bronze then switching to silver will almost seem like cheating. Starting with bronze will make you a better builder, in my humble opinion.
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Old 07-01-09, 09:20 AM   #5
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I have found greater success, cleaner shorelines, and easier cleanup using the Gasflux blue Type "B" paste. You can get it from Henry James by the one pound tub. You might also want to get a pound of the c-04 1/6" rod and see if that doesn't help as well. .
I'll put in another vote for the Type B paste flux. Definitely worthwhile.
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Old 07-01-09, 12:42 PM   #6
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The Gasflux Type B blue paste is for brass/bronze? And you brush it on like any other paste rather than with an inline fluxer? I`m using an Aesop white paste that dries out a lot and it`s a PITA to break up the little chuncks every time. I`ve never tried any other fluxes, but when this can runs out I want to try something a little easier to deal with.
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Old 07-01-09, 12:51 PM   #7
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Yes, the type B flux is a paste that you brush on like any other paste. The only difference I have noticed is that the flux is more apt to separate as it sits in the jar so you have to mix it up before using each time. No biggie.

Gasflux does also offer an inline liquid flux to run in their Gasfluxer but that is not the paste flux I am talking about.
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Old 07-01-09, 04:20 PM   #8
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you can ger clean lug brass brazing

it is about
use a big flame
not a small intense hot flame
you move quick
you flow from one point over a large area
spill over is because the lug is hotter than than the tube [it will flow first and fastest to the hottest area**
you have to get lug and tube to the same temp
and keep the large flame moving about
and get the angle of the rod so the flame just kisses it or a blob melts off onto your lug
practice and more time
Flux.
"Comwelds brass and copper flux", redishpink stuff. Good Stuff, we have it down under and in the UK
In the old days they used just straight Boric acid fluxes, it was yuk.
Harris green stuff is good by all accounts by the pros in the USA

and there is no need for a gas fluxer blah blah.
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Old 07-03-09, 10:26 PM   #9
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You might be using too much heat. Brass simply won't flow to areas that aren't hot enough and if you're flowing into areas you don't want, it's too hot. What happens to a lot of people is that they don't have even enough heat spread, so they use more of it, but they don't move it around enough. You end up with cold spots and hot spots. The hot spots end up with too much brass flowing to it and the extra collects as blobs.

Practice "leading" the brass with the flame; making it flow where you want it and away from where you don't want it.
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Old 07-06-09, 08:19 AM   #10
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Most investment cast lugs are a tight fit on the tube thus there is not enough clearance for brass to flow easily between the lug and tube. Even when using silver it’s often necessary to open up the lug to gain some clearance. First thing I’d do is make sure you have a fair bit of clearance between the lug and tube; .005” or so. Next thing is to use a large, lazy flame with LOTS of flux. You need to heat the lug on all sides to a uniform temperature before you start to add filler. Once you get a little flow going, use the heat to draw the brass into the clearance and fill the joint; if you add too much filler it will just spill down the outside. I’m not very experienced using brass so I don’t know how it differs with silver other than it takes quite a bit of heat with brass – you might want to use a larger tip on that torch.

Good luck,

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Old 07-06-09, 08:24 AM   #11
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How do you "open up" a lug? With a file? Emory cloth? Stretch it with the butt of a quill stem or something?
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Old 07-06-09, 11:21 AM   #12
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"not a small intense hot flame"

Speaking of which, anyone use a rosebud end. I have seen pictures of their being used, but the vast majority of makers seem to use ends designed for welding. Rosebud ends are designed to create a large flame that heats a wider area. I have one for my Meco, but have yet to try it.
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Old 07-06-09, 01:21 PM   #13
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Die grinder
or electric drill
using abrasive bands
on 1/4" shank rubber maundrel
get a collection of sizes/diameters
120 grit is good
Attached Images
File Type: jpg Cleaning lugs (Large).JPG (99.8 KB, 38 views)

Last edited by Silverbraze; 07-06-09 at 01:25 PM.
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Old 07-08-09, 09:08 PM   #14
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Thanks for the input.

I have my reasons for doing brass... Anybody with brass lug brazing experience who can answer my questions?

Two basics.

Keep the temperature up to the job. eg: secondary propane flame. As soon as it drops the brass stops flowing. You need a larger lazier flame than silver.

Brass needs room to move. I've had better results using powder mixed thinly with distilled water (keep those oxides to a minimum) and brushed on.

What are your reasons for wanting brass(or bronze for the technically correct).
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Old 07-12-09, 06:03 PM   #15
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Cheaper.

Easier for me to change lug angles using brass.
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Old 07-13-09, 03:21 PM   #16
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Cheaper.

Easier for me to change lug angles using brass.
Cheaper, maybe $50 saved in the whole build. Not much in the whole scheme of things.

Lug angle changing, by how many degrees are you changing angles by?
Silver works fine if you mod the lug angle + - 2 * if you do it right
and by playing the torch the right way, you can fill a lug if needed. Think of it like form work for pouring concrete.
Any who has built a lugged MAX frame know what I speak of.
and there are compact angle lugs available for OS and XL tube sizes if you need a sloper
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Old 07-13-09, 03:30 PM   #17
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$50 is $50!

I just want to get brass down to broaden my skills.

I tried a bigger/softer flame and it def. helped, but I still made more of a mess and had more charring that I would have hoped, which took me a long time to clean up with a file and wire wheel.

How clean can a skilled brass brazer do a lug?

Any more tips?
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Old 07-13-09, 05:38 PM   #18
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About that $50....
You`re obviously talking about the price difference for somebody who`s already melted a few grand worth of the stuff. I`ve been practicing with $50 worth of LFB and flux for a long time now. How many practice brazes do you get out of $50 worth of silver?
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Old 07-13-09, 08:20 PM   #19
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About that $50....
You`re obviously talking about the price difference for somebody who`s already melted a few grand worth of the stuff. I`ve been practicing with $50 worth of LFB and flux for a long time now. How many practice brazes do you get out of $50 worth of silver?
Point noted

about how clean one can braze with brass,
as neat an clean as any proffie can with silver
No charred flux and no spills
get the fit ups sweet
big flame and go fast {flux cannot be worked for too long, no matter what the temp**
the real secret is to be doing it all day, joint after joint
boring repetition work
after a three weeks, bingo
yeah, I know, that is hard to do today, as getting a job in frame shops is almost finished

I grew up with brass, starting 30 years ago
I reckon I am still neater with brass then with silver,
but prefer silver for other reasons
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Old 07-14-09, 07:37 AM   #20
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Dazza gives good and sound advice.
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Old 07-14-09, 10:59 AM   #21
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Point noted

about how clean one can braze with brass,
as neat an clean as any proffie can with silver
No charred flux and no spills
get the fit ups sweet
big flame and go fast {flux cannot be worked for too long, no matter what the temp**
the real secret is to be doing it all day, joint after joint
boring repetition work
after a three weeks, bingo
yeah, I know, that is hard to do today, as getting a job in frame shops is almost finished
I am no frame builder, can barely braze. But one thing I have learned from a variety of trades is that you are really no good at anything until you reach the point that you are becoming bored with it. Until you're tired of it (brazing, building electronics, whatever) you are probably pretty bad at it. The answer is to work at it enough that the repetitive things become ordinary and tedious and then fall back in love with the thing that got you started (beautiful frames, great sounding audio, whatever).

But first do it til you're sick of it. then take pride in it.
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Old 07-15-09, 02:39 PM   #22
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I am using a larger and softer flame that I was before, which has really helped.

But I am still getting more charring and more of a mess than I would like and its really frustrating! The brass ends up bumpy on the tube around the lug, why is that?

Am I overheating? Is it possible that my torch is dirty and contaminating things?

More help please!
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