Capping a Seatstay

I got asked how it is I create the fluted ends on my seatstays. I struggled to explain it in a 5-minute, spoken-only venue and struggled a bit. Seeing as just the night before I had photographed the process, I put myself in a position to write this post.

Starting out, I have a pair of seatstays. I find a piece of scrap tubing (you do save your scrap tubes, right?) that will become the caps themselves. Then, I figure out how I’m going to miter the seatstays to fit the caps and do it.

Roughed-in miter.

The miters — as with most others, are roughed-in with shears, and then are fine-tuned with hand files, until the desired fit is achieved. Then everything is prepped for brazing — sanding down the surfaces and making sure the materials have nothing on them that won’t contaminate the brazing. Once it’s coated with flux, I put it in a vise (gently) and braze around the edges. Because the seatstays will be attached to the frame with 45% cad-free silver, which has a low melting point, I use low-fuming bronze to attach the caps. This prevents the caps from popping loose when they’re attached to the frame, as bronze has a much higher melting temperature.

Brazing the half-tube to the seatstay.

Once the brazing is done and I’ve soaked off the flux (it turns into a hard glassy substance that dissolves in hot water), the next step is, using the shears again, to carefully trim the excess material from the tubing.

Using shears to carefully remove excess materials from the cap.

Then I put it in the vise and start in with the files. Basically the trick is to let the file follow the curve of the seatstay. As you do, the excess material falls away.

Starting to file off excess material.

And then I keep at it, working my way around the circumference of the seatstay.

Keep filing. Stream music from the iPad while you're at it.

By the time you’ve gone around the entire circumference, all the excess material will be gone, and you’ll have this:

Finished seatstay cap.