I am a frame builder AMA

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  • Any questions people have about anything fab related, from machines, to process to tubes to drawing goes here. Anyone can ask, anyone can answer.

  • How did you first start? Did a course? Or just picked up a torch and gave gluing some metal together a go?

  • Where do you get the raw material for the pencil wishbone stays you do at talbot? it's not standard diameter tubing, that you'd be able to get in a normal tubeset, is it?

  • Bought a load of shit tubes and made numerous terrible bikes for myself and friends. I never paid attention to anything at school so had very little hope that I'd learn anything on a course ;)

  • It's T45 tubing made to my spec, then formed at our workshop.

  • Great, whats easiest to start practicing, lugs or fillets?
    And as mentioned in the other thread. For home novice practice, a Mapp torch is ok for silver brazing but not brass, and silver is a bit harder to get right, that correct?
    What would you suggest to cheaply give it a bash? Not bothered with jigs and angles, just want to actually join two chunks of metal together
    Some sort of torch, gas, brazing rod, flux. That it? (in materials, exc safety equipment)

  • Bet you regret saying ANY question now

  • Yes but annoying Matt is free

  • Is steel real?

  • Yes but annoying Matt is free

    I used to think that too...

  • Lugs can both pull in more brass/solder and sink more heat, making them harder/slower/expensiver to unpick for mistakes or practice.

    Using lugs is easier since you ideally have the tube diameters the lugs were designed for, just need to get the lengths right. You are restricted in terms of both overall geometry and detail geometry, for clearances.

    Filleting tubes gives you a lot of freedom, but you'll need to make sure the curves each end are aligned properly. Assuming the ends are correct though, if you get your jig setup wrong (e.g downtube-seattube angle slightly off could result in your toptube and headtube not meeting) you can still separate the tubes and redo earlier joints (assuming you don't overheat a fancy tube and ruin the heat treatment).

  • #metallurgy

    I have previously used SIF 101, but I have the option of using Silicon Bronze CZ6 for a lot less £££.
    I have no issues with getting nice fillets and the bits I have built (including bike repairs) using it have been great. But what is the actual differences in strength? Will I die?

    BLACK BARS = SIF 101


    2 Attachments

    • Other.PNG
    • SIF101.PNG
  • Lugs if you want to build a bike, as you can easily build a frame without a jig, brazing you will at least need some sort of flat surface, theoretical at least (see what @s.walrus is doing in this regard.

  • Don't have room for a milling machine in my workshop, what's the next best thing? A tube notcher and a pillar drill?

    I used printmymitre website to make my cargo bike, but its not brilliant..

  • Lugs are easier, not least because they hold everything in place while you wave a torch around while poking yourself in the face with some welding rod. However, due to the amount of metal you need a torch with some serious ooomph. It's not so much the temperature of the flame, as the total amount of heat it can chuck out.

    Fillets are harder to do, particularly with silver. The hard thing about silver is that when it melts its very runny, almost like water. Overheat a brass fillet and it'll get a bit saggy. Overheat a silver fillet and you'll end up with a little puddle of silver on the floor. You also need to be much more careful with cleanliness and contamination with silver. If you cook the flux then it's game over, start again - brass is far more resilient to a bit of overheating.

    The downside with brass is again the extra heat required. You can add little braze-ons using silver with nothing more sophisticated than a standard plumber's blowtorch. Doing lugged joints with brass is going to require oxy-propane or oxy-acetylene like @coldharbour says.

    If you just want to stick some stuff together, I'd suggest just getting a blowtorch and a small quantity of silver and flux, something like a bit of Fillet Pro from Ceeway and some System 48 flux. You won't be able to build a frame using it, but it'll be good practice anyway with little capital outlay.

    Then once you've upgraded to oxy kit, get some practice tubes and lugs from Ceeway and do a load of them. Then move onto your first lugged frame and you're away...

  • Top advice. Thanks for your reply
    I might go for the sticking stuff together route for practice, then as you said, invest and get some practice tubes etc

  • If you've got space for a pillar drill, you've got space for a little milling machine surely? If you're looking to do mitres with a machine rather than by hand then I'd recommend a tube notcher. I've got one like this which I use for making car wishbones and ARBs. It's OK, but given the use of bushings in the sliding shaft it's never going to be that accurate and there's a good chance it'll snag if you're using very thin, very hard steel. I might using it for a rough cut on Zona, but I'd expect to have to finish it off by hand to get a really good mitre, and I wouldn't even try using it on thin-walled stainless or higher end tubing.

  • Start with two bits of wire and a soldering iron :)

  • Question - what's your dream, money no object tooling set up?

  • Hmmm, everything in the Anvil catelogue, a 5-axis CNC milling machine, a bigger lathe and a hydraulic CNC tube bender. Oh, and a waterjet cutter. I'd also like a new TIG machine, with a few more settings such as pulse and slope changes. DC only though, the current one's fine for aluminium.

  • Haha I can solder just fine with an iron, I want to jump in at the deep end* and braze bits to my bike

    *slighty deeper than the shallow end

  • You can definitely do that with a blowtorch and some Fillet Pro. I added a braze-on and filled a small dent using Fillet Pro and a plumber's torch on one of my frames.

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I am a frame builder AMA

Posted by Avatar for coldharbour @coldharbour

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