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  1. #1
    EPP
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    Lug shoreline cleanup

    What methods do people use to tidy up the shorelines of lugs after brazing? How tidy should I expect to be right after brazing? I've been practicing with some cheap lugs and am trying to get the hang of how much silver to feed in.

    Some of the examples I've seen here and elsewhere on the web look like no filing was required...

  2. #2
    Senior Member mudboy's Avatar
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    Once you've got the hang of it, you're right, very little cleanup should be required. Until you get the hang of that, your best tool is probably a set of riffler files and a set of needle files.

    Pete
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  3. #3
    tuz
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    Yes you can use files or scrapers. Also, after you flowed the joint you can try to clean up glops by bringing the flame back at the shoreline and flow it around. But yeah I think the experienced guys know just went to stop adding filler in order to get a flowed joint and tidy shoreline!
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  4. #4
    framebuilder
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    With proper technique you should be able to have crisp shorelines without the need for any filing right from the start. The three students that are presently in my framebuilding class were able to do this (have perfect shorelines) on their first frame they brazed together this last Thursday. It is also one of the hardest things about brazing to get the hang of at first.

    Good shorelines begins with a close fit between the lug and the tube. If there are gaps caused by using a lug with a different angle, a loose fit, or carelessly wiggling the tubes into the lugs during assembly, it is necessary to close them up before brazing. If you don't do this then the silver will likely shrink away from the gap as it cools. It looks ugly and says to everyone that you are a beginner.

    Second, you need someplace for the extra silver to go. On the head lugs it would be the head tube sticking beyond the lugs and on the seat lug it would be the extra seat tube length poking above the seat lug. I call this tubing sticking out beyond the lugs the "dumping ground" where excess silver can go and be cut off later. It isn't so much about melting the perfect amount of silver (so as not put the tiniest too much on) but rather knowing how to get it to this extra tubing to be cut off later.

    Third, I ran my torch over the shoreline after an area has been filled to see if there are any gaps or extra silver. If I am doing a down tube lug, I fill the down tube part first and direct any extra out onto the head tube. After filling that part, I run my flame over the down tube shorelines to see that they are perfect. Any extra is directed in a channel I create to get it onto the head tube. Once I have filled all the area of the head tube, I again run my torch over the head tube shorelines directing any extra towards the front band. It is this part of the lug that accepts the extra silver and, if there is too much total, it will be easy to flow it from the top of the band to the bottom – where it will be cut off latter (the “dumping ground”). The Curt Goodrich technique is to flow any extra from the other lug areas onto this front band and what little extra needs to be added, do it from the area to be cut off so that the perfect amount is used without a drop of waste.

    What students have a hard time doing at first is matching the speed of moving the torch with the speed at which the silver will melt and flow when cleaning shorelines. It is not just the speed they have have to keep track of but also the distance, direction (angle) and accuracy of the position of the flame. Everyone seems to have a tendency of going too slow at first and too fast at the end. Good brazing technique depends on reading the indicators at the joint and responding naturally to them without having to think of what you are doing.

    Actually there is a lot more information then this brief outline provides on how to braze lugs. I have 8 pages of techniques in my framebuilding class manual and I talk about a lot more in class. And of course an instructor proving feedback while brazing is the best and fastest way to learn. Frankly I want my students to have a competitive knowledge advantage over other beginners and do good work right from the start. Poorly made stuff can hang around a long time to represent what you do.

    Doug Fattic
    Niles, Michigan

  5. #5
    EPP
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    Thanks for your responses everyone, I had started to realise that it was possible to clean up and area by running the torch back over it, but it's always nice to get confirmation one is doing the right thing.

    Doug! You might not remember me - I was trying to get started with a framebuilding project about 6 years ago (can't believe it was that long), and you took the time to answer many of my questions. I think we got in touch via the framebuilders list. You were about to embark on an overseas framebuilding project - I think you wanted to teach communities to build practical bicycles for everyday use.

    My job, moving house, getting married etc. sort of took over though, and it was proving too difficult to get hold of gases for the brazing torch and the project came to an end. But I have recently seen some videos of people using mapp gas to braze with silver, and my enthusiasm has been renewed! It also helps that I have a cellar with a workshop, so have the space to work in now. I bought a turbo torch that I've discovered is plenty hot enough for brass as well as silver and the map pro gas is freely available from the local hardware superstore (and it doesn't void my house insurance!). Some people say it's not quite as good as oxy acetylene, but it's all I can access for the time being.

    I still have copies of the emails you sent, and I'll be looking them out as I progress. I had been planning to get in touch with you just to say thanks again for the advice you gave me all those years ago - it was not wasted. You were very generous with your knowledge

    Your description of how to flow the silver neatly around the lug was very helpful, especially the idea of having a dumping ground to collect to the excess. I'm going to keep practicing, but will hopefully be moving on to my first frame (a compact lugged road frame) soon. I have been achieving some nice results with small fillets of silver when brazing bits of scrap stays to larger diameter tubing. I'm hoping this will pay off when I come to brazing the seat stays to the seat lug on the frame.

    I'd like to produce a photo diary of the build to post here, as others have done.

    Cheers, Ewan (Manchester, UK)

  6. #6
    EPP
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    Just been practicing brazing quarter sections of tube onto another tube. Am finding that I'm scorching the flux on the top of the piece being brazed, but seem to be flowing the silver pretty well to all edges and achieving neat shorelines. I'm finding that, generally, I seem to have to heat any joint i'm doing up to a temperature that scorches some of the flux before the silver flows well. Is this just a symptom of a newbie being clumsy with the torch?!

    I'll see if I can post a pic or two of some practice joints...

  7. #7
    EPP
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    Just after brazing:
    DSC_1658..jpg
    DSC_1660..jpg

    After a quick cleanup:

    DSC_1669..jpg
    DSC_1671..jpg

    Another attempt after brazing:
    DSC_1672..jpg

    And after cleanup:
    DSC_1674..jpg
    DSC_1676..jpg

    And another joint after quick cleanup. I got this up to just the right temperature and flowed the right amount of silver around the junction. By moving the flame around I was able to smooth out the silver so it was evenly distributed. This is how the bridges will be done, and by adding more silver I have been able to produce small fillets that will look good where the seat stays join the seat lug:
    DSC_1667..jpg

    A joint that didn't go so well:
    DSC_1679..jpg


    I sliced through the tube to check penetration on some joints I did at the end of the tube earlier this week. They weren't tidy at the edges, but I just wanted to see if the silver had flowed properly. It's just possible to see a thin line of silver between the layers of steel:
    DSC_1681..jpg

    So, it looks like I tend to scorch the flux just as I add silver at one corner of the joint for the first time (see the bottom right corner of each 'patch' i've brazed). As I move the torch around to draw the silver across the joint I'm beginning to be able to hold it at the right temperature, and even add extra silver without overheating if there isn't enough to draw through. Why I can't get this temperature right initially, I don't know. I think part of the problem is also that I return to the first corner with the torch to flow any excess silver and draw it across, so this area gets more heat. The blackened circle on the patch is when a bolt was clamped down to hold the patch flush. This acted as a heat sink and scorched the flux around it.

    I'd ideally like the whole patch to end up with a glassy covering of flux with no scorching. I'm going to be ordering frame parts from Ceeway soon and will buy some cheap lugs to practice with. I've used some nasty pressed ones but want a couple of cast ones that are closer to what I'll be using on the frame.

    Bear in mind that this is with a mapp torch with the flame held a good few inches from the metal. It does produce a lot of heat, which goes against what I've read pretty much anywhere else on the web.

    Any suggestions for improving technique are welcome!

    Ewan

  8. #8
    Randomhead
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    from what I've seen, a lot of people have problems with overheating with MAPP. Which does seem to be backwards given that it's not as energetic as O/A

  9. #9
    tuz
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    Yes I think the flux scorching comes from the lower heating power. If I remember right, flux is only active during a certain amount of time until it saturates with oxides. Since with air-mapp you have to heat for a longer time to get at temperature...

    EPP, I was also reluctant to use compressed oxy-acet gases. Based on the experience of BF member Papa, my setup is with a medical oxygen concentrator and a BBQ propane tank. Works well so far. A bit safer from not having compressed oxy.
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  10. #10
    EPP
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    That's worth knowing that the the flux remains active for a limited time. I've been deliberately heating the joint slowly and moving the flame around lots in order to bring more of it up to temperature in one go as I have read of other people's success with slower heating. I'm holding the tip of the torch about 2-3 inches from the joint as any closer to the hottest part of the flame results in (for me at least) an uncontrollable increase in temperature.

    Maybe better technique will allow me to bring everything up to temp quickly, get the silver in, flow it round and get the torch out. I'll certainly try this out.

    I may try posting a recording of my brazing efforts on youtube - I'm sure someone experienced would pretty quickly pick up on obviously poor technique!

    Hmmm, maybe this is daft question (I'm no chemist), but does powdered silver brazing flux have a shelf life? Mine sat unopened for 6 years in my workshop before I got round to having a go at this framebuilding malarkey!

  11. #11
    Senior Member mudboy's Avatar
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    Aside from photo 9, everything looks pretty good to me. Have you tried brown flux? I only use white for small stuff like braze-ons.

    Pete
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  12. #12
    EPP
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    Quote Originally Posted by mudboy View Post
    Aside from photo 9, everything looks pretty good to me. Have you tried brown flux? I only use white for small stuff like braze-ons.

    Pete
    I've only got the white stuff, and the pink sifbronze for brass. What's the difference between the white and brown flux?

  13. #13
    Randomhead
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    my experience is that if you have the heat right, flux will last an amazingly long time. I think with MAPP you're going to have to learn to live with some compromises. The propane/air concentrator setup would be really nice, but I think they are hard to find at a reasonable price

    I only count 7 photos. I wouldn't say the brazing looks good, but it looks like it is structurally sound.

  14. #14
    EPP
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    Quote Originally Posted by unterhausen View Post
    I wouldn't say the brazing looks good, but it looks like it is structurally sound.
    A fair appraisal!

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