Originally Posted by
LHthread
Thanks Doug. It's good to know the heat can stay local enough to each joint location. In my normal work, I'm brazing with anything from a rosebud to a #1 and hardly think about it, but a bicycle frame is like a musical instrument, and I'm a bit apprehensive about getting things as right as I can. Regarding Reynolds 753, I was under the assumption that some amount of cold setting was part of the deal. Are you saying that when using heat treated tubing one has to nail the alignment all through the process? I'm planning on using 531 for my first frame, by the way, as it seems like a more forgiving alloy for a beginner. That's a funny story about the Americans failing the test. The Brits are top notch craftsmen, and there's not a very strong master/apprentice relationship here. But we are good at banging things out, or we used to be, anyway.
The 753 test needs to be put into context. 531 frames sold for small money after WWII in the UK. I bought my Hetchins frame for $75 in 1969. The market for 10 speed bicycles was to the poorly paid working class. A builder had to work fast and make at least one a day to make a living. They probably worked for a shop or shops that typically didn't have any expensive tooling. Frame alignment would probably be after the build. 531 would bend nicely.
Adult Americans didn't ride bicycles until 1970/71 when suddenly interest exploded. People that now wanted to build frames had to ether go to Europe where there were a lot of builders or try and figure it out on their own. Neither of those situations were ideal for knowing how to silver braze heat treated tubing (higher temperature melting brass would reduce the heat treatment). This is why Reynolds wanted to protect their new flagship tubing from getting its reputation ruined by a culture of inadequate techniques.
Americans in the 1970's were marketing to a different social class with a lot more money. They could charge more and as a result spend more time on each frame. It wasn't long before Americans did figure it out but it wan't right when 753 was introduced.
But to answer you question, yes thin wall heat treated tubing can be cold set a little during the build. Small adjustments can be made between spotting and brazing each joint. I've always considered myself to be very fortunate to have gone to a place in England that aligned on a cast iron surface plate during the build rather than just after it was made. That was good preparation for heat treated tubing when it became available.