Thursday, April 28, 2011

Joining Practice

Me and the 2 people working on frame building all practiced our respective joining techniques in the metal shop today. I was working with brazed lugging while the other two worked on fillet brazing and TIG welding. I also tried oxy-acetlyne welding today as part of my metalworking homework. Here are some photos.

This is a pretty poor attempt at lugging. Brass, a softer metal than steel with a higher melting point, moves toward the hottest part of the steel. The trick is to heat up the part of the steel you want the brass to move to while also pushing the brass towards that specified area. This means a bit of going back and forth between points while keeping the brass on the track you want it. I learned all of this as I was going along, so hopefully future attempts won't be so dirty and sloppy...

A look at the inside... You would ultimately like to see the brass seeping out of the other end of the tubing, though I probably inserted the tube too far for the brass to travel. Either that, or I'm just bad at controlling the flow...
This is a oxy-acetlyne welded form that I made out of scrap 16 gauge sheet metal. Steel of course. I'm way better at oxy-acetlyne welding than brazing, but I guess I also have way more guidance and experience with it.
Scrap tubing donated by Bill Stevenson, a local frame builder here in Olympia, WA.
Fillet brazing. Depending on technique, the brass can really build up trying to weld the two tubes together. To get the desired aesthetic, it seemed smart to grind down the brass with a file or circular grinder.
Here is the result. Fillet brazing is considered inferior to TIG welding because you're more gluing two pieces of metal together with a different kind of metal rather than fusing them together. But both are plenty strong to withstand the loads bicycles take on for the most part. I'll go more into the benefits of certain joining techniques in a later post.
TIG welding in action.
TIG welding. Most steel frames that you encounter today are joined though this method, such as Surly's or Somas. Only curmudgeonly dated cranks bother with brazing these days; such as myself. There are reason though, promise!
Fillet brazing and TIG welding in one dummy frame.

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