SF Cyclotouring: UBI Framebuilding Class

5/12/2015 - Day 2

Deburr & clean joint
A Feedback workstand is especially good for brazing because the clamp allows you to adjust the tension loosely and rotate the work around for 360° access
Heat warps tubes -- especially at the end of a tube
Position joint 15-20mm from the end of a tube
Scotchbrite the brass filler rod to clean it
Tack on obtuse angle at the centerline
Tinning seals up the seam
Heat the steel to just barely orange
Leverage gravity to get the brass to move where you want it to

Socket & Plug-style dropouts limit which seat- or chain-stay tubes you can use, since the diameters must match
Tab-style dropouts are much more flexible -- nearly any tube diameter can work

Deburr inside of tube
Tab for dropout should be 6-8mm deep
Measure the ID of the tube (11mm)
Measure width of dropout tab (14mm)
14mm - 11mm = 3mm / 2 = 1.5mm needs to be removed from each side of the tab to fit inside the tube
Scribe with caliper to show width of tab
Scribe depth on tab with caliper
Measure thickness of tab metal and scribe onto tube (5mm)
Use hacksaw to cut slot in tube; cut to inside of your scribe marks
Break chunks out with needle-nose pliers
Use warding file to clean up the slot
Clean up and align tab to slot
Clean out inside of tube with emery cloth wrapped around a round file
Cut tab to fit with hacksaw
Use large file to adjust tab fit; round the sides to mate with the tube ID
Clean tab with emery cloth
Clamp practice joint in vise, with tab pointing up

Use brass flux and filler
Use a full stick of brass for this practice -- half a stick per dropout joint
Heat the tab mainly, then "brush" the torch downward onto the tube
Tack at the corners to prevent/protect from overheating
Seal the joint by flowing brass between the corners and around the outside edges of the tab
Move torch around to heat tab evenly
Fill up the gap on sides of tab to create a brass plug -- watch for shrinking as brass cools and solidifies
Add a nice fillet at the top to cap the joint