Tuesday, 10 May 2011
I confess this is probably my favorite part of framebuilding; where I get to play around with the lugs and make them look right.
I started by quickly filing and sanding the casting roughness from the derailleur tab and STI cable bosses. There wasn't any real modification done to these, save to file the loveheart cutout on the STI bosses into a rounded triangle, so that it matches the other lug cutouts I plan for the frame.
Next I removed the rack mounts from the dropouts, and cut some small triangles into them. As with the other stainless parts, much of the casting roughness has been files off and I've hit them with some emery. Once they're on the chainstays, I'll do some more serious sanding and polishing.
Finally I went to work on the lower head lug. I first cut a triangular cutout in the tang, and then removed the cast-in STI bosses. They looked a little full then, so I cut more triangles in where the STI bosses had been, and rounded the sides a little. I'm quite happy with the look now.
Next step is to replicate the cutouts and shaping on the upper head lug, and then decide what I want to do with the seat lug.
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Can't wait to see what this frame turns out like....! What tools do you use for cutting such tidy triangles out the lugs?
Good question! It depends on the dimensions and shape of the cutout as to what tools I use.
For these (large) ones, I started by drilling 3mm holes in the drill press just in from the corners of the triangle, so the hole comes to about 0.5mm from the edge of the cutout.
Then I make a 3mm hole in the center using the drill press, and enlarge it until it overlaps the other holes, or comes close to an edge.
All the finish work is done with files - mainly a set of key files. These are slightly larger than a needle file, but smaller than a normal file. My set is from Pferd: http://www.pferdusa.com/products/201a/201a15/201a150803P.html
These files are really nice for this work - they're a Swiss 2 cut, which is equivalent to a smooth American cut file, but rougher than most needle files. In any case, they make short work of lugs.
So when cutting with the files, I start with the corners, by extending the hole I made with the drill press to the corner with a 3mm dia file. Then I use either a tringle or flat file to bring the sides down to meet the corners.
I finish with needle files, as they leave a much smoother edge.
It's heaps of fun, and very relaxing work.
Awesome, thanks Suzy.
I have just sent my first frame to paint, and am eagerly planning the next. It is quite addictive!
Susy ....... great work on Ben's bike. I am sure he will be delighted.
Keep up the great work and blog. rich (La Crosse, WI USA)
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