Filed In: Process
Father/Daughter Project - Part 17
Friday, February 7, 2020 | Chris Blandford
1. Miter Stem Pieces
2. Tack and Braze Stem
3. Finish Fillets
4. Braze Binders
5. Slot and Relieve Binders
I’ve only made a couple of stems like this one previously, but the process has been straightforward.
I begin by designing the stem in BikeCAD, printing the miter templates, and mitering the stem’s main tube. This tube is, essentially, a very short downtube; I miter it exactly as described previously. The other tubes (both made out of .058” tubing) are cut to length and squared up on my belt sander. I leave the tube that clamps onto the steerer long so that I can grab it while brazing. I’ll trim it to length once the binders are brazed on.
Once mitered, I drill vent holes in the clamping tubes, clean, flux, and load the tubes into a stem jig (Sputnik). I tack the stem together in the jig (obtuse angle first, as before), let cool, then pull the stem from the fixture. To braze, I clamp the stem onto a longer length of tubing.
Braze, let cool, and then soak.
Next I finish the areas of the fillets closest to where the binders will land. Then I miter and notch the binders (just like I did with the seat tube binder), clean, flux, and (bronze) braze them on. Soak once more. Finally, I drill a pucker hole in the steerer-clamping tube and slot both binders with a hacksaw and flat files. I also file a little half-round relief in the binders where they pinch together. At last I trim everything to length and finish any remaining fillets. I also shape the handlebar clamping tube a bit, to make sure that the handlebars’ curves--when installed--run through easily.
The final thing I did for this stem was run a flex-hone (chucked up in my cordless drill) through both clamping tubes. Then I installed the stem and handlebars and checked that all went according to plan. All good this time around.
(This reminds me… I’m not sure if I mentioned before: a seatpost of the correct diameter fit nicely into this bike’s frame, which I checked back when I was finishing off that binder/slot. I didn’t bother reaming the seat tube on this bike. There, too, I merely used a flex-hone to finish it off.)
Next up: final touches and off to paint!