Cleaning up the braze

[BigPoser]

Might be a silly question, but how do you all clean up the lugs/material after brazing? Seems it'd be tough to get a BB lug in on a grinder with a wire wheel. Looking for specific ways since I'm trying to build up my tool inventory.

Thanks!

Brandon

[Curt Goodrich]

Sandblaster filled with 80 grit aluminum oxide is my preferred method.

[Andrew R Stewart]

I think it depends on where and how much the excess filler is or where the socket finishing needs are. If there's no added build up, globs, your lug surfaces are already finished prior to brazing, if you braze cleanly... then a media blasting may be all that you feel is needed. With a builder of Curt's experience I would expect this likelihood.

But for those of us who are less skilled- we use various tools. Some power like belt sanders, Dremels, 1/4" die grinders, bench grinders and a lot of hand steps with files of varying shapes and cuts, production cloth of various grits, scrapers (great for lug edges). What I don't use are wire wheels and abrasive pads.

Doing the clean up and finishing brings a strong motivation to get better at brazing. I'd rather braze cleaner then have to file/sand. Andy

[devlin]

I use a timber handled stainless wire brush. 4 rows is my favourite at the moment. I try super hard to make sure there are no blobs but they happen and then it's as Andrew said, files and shop roll and shaped bits of dowel and square timber. I even find shop roll with ice cream sticks really handy for cleaning up the inside curves in some spots. A few times I have used a very tiny flame to draw that little bit of excess along to and outside curve and try and flick it away or leave it in a spot I can file it easier.

[TurboTom]

I use various grades of sandpaper "tape" that I have thumb pressure on the spot and pull with my other hand. Silver is easy but it works fine with brass too. And, I'm a total neophyte! I'm not cleared too used files or other "faster" methods yet.

[rellis]

Wire wheels chucked into a hand drill will take a lot of residue. Wear face protection.

[Martin T]

As Curt was implying and Tom Kellogg once said your goal should be to braze the joint so there is no clean up. If you are beginning or don't have a torch in your hand every day that's not a reasonable expectation, but with practice you can get there. Learn how much filler you need to complete a joint and don't over fill. If you do find you have more filler than you need, move the filler while the joint is hot. It takes some experience to be able to see thru the flux to determine whether or not you have a cold stop. Use the rod to wipe away molten flux from the edges so you can see the filler meniscus better.
There are lots of riffler files out there that will give you a nice square lug edge, but that takes labor. If you look up riffler files on McMaster take a look at Trade Nos 5 and 6. Those are good for squaring edges. And when filing, do your best to stay on the filler and off the tube. Power tools have their place, but cleaning up lugs is not their forte.

[Doug Fattic]

Brazing clean shorelines is possible on a first frame with proper instructions so there is no need for any further cleanup. I expect every one of my framebuilding class students to build their frames with very little to no silver poking out beyond the lugs. It is only for those whose hand coordination is on the very left of the Bell Curve that I have to help achieve this goal.

Clean shorelines start with a proper lug to tube fit. If there is too much or too little of a gap between the two then there will be problems. With too much gap (caused by too big a socket or a changed angle), there probably will be a void and – when trying to fill it – silver won’t stay there and will run away creating a glob somewhere else. Also, silver won’t flow through a tight fit and then it will just pile up on the shoreline with no place to go. For example this can be caused when the chain stays are held at a different angle than the bottom bracket shell's.

Here are a couple of methods to help get clean shorelines. 1st have extra tube sticking out beyond the lugs where extra silver can go. Start brazing farthest away drawing silver to it. This way you don’t have to be impossibly exact in how much silver to melt. And that extra tubing and silver will be cut off later. 2nd it is possible to pinpoint your flame right on the shoreline and with the help of gravity flow it in a wave (like riding a surfboard) toward an exit.

Specific detailed instructions of brazing clean shorelines is more than I want to write in this subject thread. It is easiest to understand when seeing an actual demonstration. And I like my students to have some knowledge advantages.

[Michael Gordon]

Brandon,

Thanks for posting this question. A lot of great comments have been posted, but they seem to be addressing a wide range of conditions.

Can you post a picture that relates to your original post?

[BigPoser]

Thank you guys! I really appreciate the tips and comments. So I'm just practicing now with sleeves and am trying to get it down before I try on an actual lug. I can get the brass all the way through the material, but the outer sleeve ends up black, which leads me to believe that I'm using too much heat (paired with a lack of torch experience), and am exhausting the flux. Obviously when cleaning everything up, I can't just go for it or I'll end up thinning the walls or worse.

Should I be using silver rather than brass at first? My thought for using brass, is that it is more difficult to learn than silver, so if I get it down, brazing silver would be that much easier.

I am using an oxyacetylene rig with a #4 tip, if that helps.Braze.JPG

[Andrew R Stewart]

Brandon- Are you fluxing the outside too? Some will say that anywhere you apply the flame should be fluxed. Andy

[Doug Fattic]

My philosophy of teaching framebuilding is to start with the easy stuff and as mastery is gained do more difficult things. It is easy to get discouraged and not be sure which variable is causing a problem. I find it better to start with silver on a simple sleeve. This allows the student to become familiar with moving the flame at the right distance, speed and angle brazing something not difficult to do. Once he/she is able to keep those flame variables constant without having to consciously think much about them, then the proper pattern over a more complex joint can be considered.

[Paul Jacobs]

Those appear to be quite long sleeves. With most lugs you don't have to draw the filler so far for 360 degrees around the tube or even with most fork crowns.

[BigPoser]

Hi Andy,

Yes I flux it up everywhere.

[BigPoser]

Doug,

Thank you for the comment. It certainly makes sense. I'll have to give silver a go.

FYI, I'm planning on coming to your school next year. I'm a bit early in planning, but that's the goal.

[BigPoser]

Those appear to be quite long sleeves. With most lugs you don't have to draw the filler so far for 360 degrees around the tube or even with most fork crowns.

Yes, you are totally right. I'm probably doing a lot more than I'll ever really need to, but I thought it would help me more.

[Doug Fattic]

Brandon, I look forward to you coming! Here are some of my thoughts on learning how to braze. The end goal of brazing is to be able to bring a joint up to the proper melting temperature and keep it within that window while adding the filler without having to think much about your flame motion. When you finally “get it”, your hands will move automatically to place/move brass (actually bronze) or silver where you want it to go. You adjust your flame pattern instinctively as you see what is happening. If you were to ask a pro how they braze a particular joint, they would probably have to pause and act it out so they would know how to answer. They would have to think how to describe the particulars because they do those things by instinct. This is why not every expert is a good teacher.

Your goal when you 1st start practicing is to just get used to holding and moving the torch/flame so it feels natural while you stay relaxed. It makes sense to work on one variable at a time (like distance) until you can be consistent about it without having to think much about it. This is why it is best to start out with a very easy braze like using silver on a short sleeve so your focus can be limited to basic fundamentals. When you have too many things to think about how to control you can’t keep track of them all and something goes wrong.

Once you become familiar with keeping the proper flame to joint distance, you can start adding other factors that control heat like the speed and angle of the flame as well as flicking it on/off. Part of your preparation (before starting a braze) will be to already know where and at what angle to place the rod and what flame pattern you will be using. That is why I suggest starting with silver on something easy to braze. Eventually those motions will become muscle memory and you will be ready to start doing something more complex.

Rookies make similar mistakes. Once you know what they are and correct against them, you have a big head start in successfully brazing. One caution about trying to learn on your own before instruction is that you can pick up bad habits that are very hard to break (since the whole point of practicing is to memorize hand motions). It can be difficult to figure out on your own what the problems are. It is only when you have a good flame pattern you don’t have to think about that you have enough observation energy left over to be able to do all the requirements of brazing a specific joint successfully.

Brazing is complex and subtle. There is very little difference between success and a mess. My class manual on brazing is 25 pages long. That includes some repetition for emphasis and saying the same thing another way for clarity. And of course several pages on equipment guidelines.

[EricKeller]

my favorite method is to use a torch. When I'm done brazing a joint, I'll look it over before turning off the torch and make sure I haven't left any ugliness anywhere on the shorelines and fix it then. I suggest you make some 1" wide sleeves and practice leaving a nice shoreline. If you have an expectation that you're going to have to go back and file, that means you probably are going to have to go back and file. There is already enough filing in frame building for my taste.