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Thread: Tig brazing... Help a brother out.

  1. #1
    Registered User fantapants's Avatar
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    Tig brazing... Help a brother out.

    Hey guys.

    So I'm getting to the point of welding a mount tab onto the block for my 3sge.

    Tig brazing has been suggested and seems to be the go.

    I have collected some 2.4 silicone bronze rods. And have my tig.

    But I'm a at a loss as to where to go in terms of starting amps etc. And if there are any fancy tricks I need to be aware of before I get blazing ? lol

    Also how clean is clean ? Like a scrub and some degreaser or a grind back to shiny and fresh ?

    Cheers for any helps lads...

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  2. #2
    This space left blank Ben Wilson's Avatar
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    I've never tried TIG brazing, but I'd have to thing (like everything TIG), completely clean would be a good starting point.
    Imagination is more important than knowledge.

  3. #3
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    Yeah grind back all the paint, degrease the shit out of the area you're welding in. I've never done tig brazing however what I remember from tafe for welding cast was to basically heat up the area you wish to weld (if you have an oxy torch that makes it easy to do). Once it's hot, start your weld. Once welding is completed, you want to control the heat in the block so it doesn't cool quickly and just crack (if you have a big fuckin oven or patience with an oxy either way).

    If you've never done it before, it's probably is a better idea to pay somebody to do it. The way they made it out at tafe, it's something that takes a bit of practice & experience to get correct. Unless the mount tab isn't mission critical and you can afford to risk it.

  4. #4
    Registered User fantapants's Avatar
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    If I don't braze the bolt onto the block, I'll just use some 10mm flat bar to pic up a different mount boss. The mount has 3 good solid mount points, the fourth is just insurance lol.

    The brazing shouldn't shock the cast any/much as it doesn't actually puddle the base metal. The block itself shouldn't ever get to a melting temp, just hot enough for the liguid bronze to glue.

    So much less chance of explosions etc (success not guaranteed lol)

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  5. #5
    Registered User Justengt4's Avatar
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    If you have 3 mounts in the block I don't think a forth brazed mount will do shit TBH...likely it'll just crack
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  6. #6
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    Cleanliness is always important.
    Use about 1/2 the current you would for tig welding similarly sized steel parts as you are not fusing the parent material when brazing.
    There's some vids on youtube with some info on tig brazing with silicon bronze rods..
    If you have ever silver soldered or brazed with an oxy, you'll be half way there..

  7. #7
    Unregistered User Permit Roadsailing's Avatar
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    you probably already subscribe to this guy's channel, but this might be worth a look

    Last edited by Roadsailing; 18-10-16 at 09:59 AM.

  8. #8
    Registered User fantapants's Avatar
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    Have watched quite a lot of his stuff but havnt seen that one. Excellent find old mate appreciate it

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  9. #9
    Registered User TRD-MX62's Avatar
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    Brazing is underrated, repaired a broken gear tooth on my brothers old G60 patrol gearbox and it outlasted the gearbox being replaced with a 5 speed!

  10. #10
    Registered User fantapants's Avatar
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    Yeah I have other options available to make this solution work, but I'm really keen to learn something new.

    So I'm keen to have a crack at brazing this nut onto the block.

    Also I'm going to have a go at tig brazing some of the bike frame stuff ...

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    Registered User dave1600's Avatar
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    Quick question (and I'm not sure if its relevant to TIG, my experience is with oxy). Are you intending / trying to do the traditional "brazing" where you get the bits to a dull red, apply the filler rod and it melts and is drawn into the joint (sort of like soldering), or what I've seen referred to as "bronze welding" - building up a fillet like a normal weld, but in this case the fillet is bronze (like the video above) ?

    Not sure how it wiltranslates to TIG, but my tips based on oxy brazing are :

    1. Cleanliness ! Everything must be spotless.

    2. Heat. Don't overdo it or you will burn the alloying metals out of the filler rod (zinc, etc). Bubbling filler and / or whitish smoke (like you get when welding gal pipe) is a sure sign its too hot and you've stuffed it. I find that a dull red in the work being joined works best. I keep heating till I think its good, take the heat away and put the brazing rod on the joint. If its hot enough, the rod will melt and "wick" into the joint. If not, apply a little more heat and try again.

    Apologies if none of this applies to TIG brazing. Keen to hear how you go !
    Last edited by dave1600; 18-10-16 at 12:39 PM.

  12. #12
    Registered User fantapants's Avatar
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    From what I can tell there is no reliance on whicking effect with tig brazing. It's essentially building the fillet...

    The only experience I have is with lugged bicycle frames where by brazing they refer to the whicking effect of drawing the molten filler into the gap and gluing the lug and tube together. Also for mounts for cables and bottle cages etc etc. It's all whicking.

    The fillet brazed bike all rely on a buildup that is then smoothed out. (not always).

    Also silver is often used, especially with stainless tubing, in the place of bronze..

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  13. #13
    Registered User dave1600's Avatar
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    In that case, I have nothing to offer !

  14. #14
    Registered User fantapants's Avatar
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    Hahha nah you have offered heaps lol

    This is all very imaginary right now. With my issues I am having trouble getting it all straight in my head. So just bouncing ideas and Shit around actually helps a lot when it comes to forcing me to clarify my own understandings.

    I'm kinda relying on winging it and it all coming together as I work on it lol (not the best policy lol)

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  15. #15
    GTFO of my ED doctor ed's Avatar
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    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
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  16. #16
    Registered User dnegative's Avatar
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    Quote 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.
    Last edited by dnegative; 18-10-16 at 07:59 PM.
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    Fuck I'm retarded

  17. #17
    Registered User fantapants's Avatar
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    Quote 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

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  18. #18
    GTFO of my ED doctor ed's Avatar
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    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"
    Last edited by doctor ed; 19-10-16 at 12:37 AM.
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  19. #19
    Registered User 9triton's Avatar
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    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.

    Last edited by 9triton; 19-10-16 at 08:24 AM.

  20. #20
    Bannered takai's Avatar
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    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
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    would be fairly easy on that pinion, I used it for some bodywork mods on my ZZE wagon frontend swap

  22. #22
    Registered User fantapants's Avatar
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    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

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  23. #23
    Bannered takai's Avatar
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    Cool, i might end up giving it a go when i get around to doing the steering rack.
    Chris
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  24. #24
    Bannered takai's Avatar
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    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
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  25. #25
    Registered User MWP's Avatar
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    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.

  26. #26
    Bannered takai's Avatar
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    Quote 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
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