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Tig brazing... Help a brother out.

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    #16
    Originally posted by doctor ed View Post
    if could tig the Joint, i dont know why youd braze it.
    Brazing is the only way to repair cast iron type material with any success and integrity; If you break some old cast pulley or part of a machine you cant get its the only way to do it.
    I've seen an engineering shop machine off a fucked acme thread of decent size on final drives where a nut holds the thing together and use half a bottle of oxygen and two dozen brazing rods building up the area before cutting a new thread. Guy doing the work was adamant the strength of the braze was more than what the cast was.

    I've seen some fucking awesome cast braze jobs, that said, all were done by old timers who cut their teeth fixing fucked shit it seems.

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      #17
      Originally posted by doctor ed View Post
      my 2c: brazing strength is dependant on the shear strength of the braze material drawn into tightly overlapping Joints. so excellent for slip Joints, overlaps, or other big surface area joins where the braze is in shear.

      using a brazing rod as a tig filler, and running a braze bead is an entirely different mechanical situation. now the tensile strength of the braze material itself become the most important factor, you have limited surface area where the braze 'keys' into the surfaces, and the surfaces are oriented at 90deg to each other (so never in shear). gut Feeling says such a Joint would be a bit dicky, and certainly nowhere near as strong as a regular tig welded Joint. if could tig the Joint, i dont know why youd braze it.

      cool old bike Frames were brazed, sure, but they used slip joints
      The video above shows how strong a good fillet braze is on bicycle tubing. The tubing buckles well be for the brazing shows any sign of stress. Generally brazing on bike frames makes a large fillet. Much much larger than a similar tig fillet. So throat thickness would be greater and overall mechanical attachment would be greater in fillet brazing vs tig. Obviously you lack the peno though.

      But especially with bike tubing, a good braze should have a higher tensile strength than the tensile strength of the tube itself. Bearing in mind bike tubing is usually around .65 mm thick.

      Currently fillet brazing is hugely popular in the custom bike game. Much more so than lugged stuff currently.

      As for why I'm doing it ... Primarily as stated above by old mate. Only way to safely weld cast iron (well not the only way but the cheapest way available to me lol) is to braze. And the work I'm doing won't be under huge strain so if I don't manage to do it stupendously well, it's not the end of the world :D

      Sent from my HTC_0P6B using Tapatalk
      RIP Carly - a smile to light the world.
      06/07/2011

      http://www.performanceforums.com/for...#post842594902 - making little toys for the big boys

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        #18
        the bike tube fillet brazing example just sounds like a case of quantity over quality. the braze material cannot compete 1:1 with steel for ultimate tensile strength. that you may lay a slug of braze down that proportionally dwarfs the steel parent material obviously makes up for that inadequancy a bit.

        but bear in mind, ist not just the material itself. a tube is strong because ist a tube. you can make it ridiculously thin becuase the strength Comes from the outer Dimension. but where do Forces concentrate? at the joins (hence double/triple butted tubing etc) so just be wary, thats all im saying.

        brazing cast shit is another Thing altogether. hence why i said "if you can tig it"
        Mit freundlichen Gre

        Originally posted by Keith Duckworth
        "I think that in a racing engine, the closer it is to disintegrating, in general the better its performance will be "

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          #19
          Norton manx frames racing were fillet brazed-and lugless.

          they were Reynolds 531 tubing -so was the only way with technology in the 50's.




          I think the spitfire engine mounts were also 531 and hence the sif bronze brazing for these prior.

          the Norton frames for the road bikes were lower grade steel and arc welded
          a manx frame

          now bespoke lugless motor bike frames are brazed for beauty.

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            #20
            fanta, did you ever do the brazing?

            I thought you had posted somewhere about brazing (might have been facebook). But now im considering it for the steering pinion.

            If you did, how did it go?
            Chris
            ------
            The new nugget
            I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

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              #21
              would be fairly easy on that pinion, I used it for some bodywork mods on my ZZE wagon frontend swap

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                #22
                I did, the Bolt held to the block when tightened (admittedly I didn't hang off it but it made no alarming noises)

                But I havent fitted the engine yet so have no idea if it will hold up #shrugs.

                I've been doing a bit of silver brazing on the bike frames for the little bits (bottle cage mounts and stuff)

                Everyone I've spoken to who tried to use tug braxe for small parts has had very poor results. Becssue it doesn't use a whicking process, it just isn't as clean or tidy as silver, and really not as easy lol.

                That being said, I'm a fat better tig welder than I am a torch man, lol. But keep practicing in hoping to improve lol

                Sent from my HTC 2PS6200 using Tapatalk
                RIP Carly - a smile to light the world.
                06/07/2011

                http://www.performanceforums.com/for...#post842594902 - making little toys for the big boys

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                  #23
                  Cool, i might end up giving it a go when i get around to doing the steering rack.
                  Chris
                  ------
                  The new nugget
                  I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

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                    #24
                    Ended up giving it a go on the steering pinion:


                    Worked pretty well, bit of contamination from stuff bubbling up from the gap that i couldnt get to, but it seems solid. Put ER70S6 tacks in the other sides too.
                    Chris
                    ------
                    The new nugget
                    I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

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                      #25
                      That looks like a weld, rather than brazing.
                      You'll have the base metal mixed with the silicone bronze filler.
                      It'll do the job there though.

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                        #26
                        Originally posted by MWP View Post
                        That looks like a weld, rather than brazing.
                        You'll have the base metal mixed with the silicone bronze filler.
                        It'll do the job there though.
                        Nah, heat too low to weld effectively. Was sizzling though from the contaminants in the gap. I did lift the torch slightly at the end too which has wicked the silicone bronze up a touch.
                        Chris
                        ------
                        The new nugget
                        I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

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