The trickiest part, so far anyway, has been the equalizer fulcrum. There was just no easy way to hold it. I made a drill template to drill the holes, and fixture to hold it during the machining process.
Make
the drill template and the fixture from the drawings. The mill cuts in
the
fixture are for clearance and therefore are not that critical. Just
locate the
holes accurately.
The first thing to do is file the back sides (the actual equalizer fulcrum, see the marks in the above picture) in order to provide a square and parallel surface to clamp in the vise. Clamp it in the vise and block it to achieve an average level and tighten the vise. Clean off the top surface where the drill template will be clamped. The mill will have to be hand cranked around the brake hanger boss. Clean enough to clear the drill template. Clamp the drill fixture on the part and drill for 10-32 tap using the back of the drill template on the vise top to keep the part square. Lightly spot the hole for the equalizer beam.
After drilling the top holes, force thread two 8-32 machine screws through the new holes, remove the clamp and drill the bottom holes.
Use the fixture as a tap guide and tap the four holes, putting a 10-32 cap screw in each hole in turn.
Clamp the part in the fixture as shown in the picture above, making sure that the screws are below the finished surface, and machine the top and back. Remember to machine the bottom tang to the same dimension as the back. I didn’t machine the whole back, just enough to clear the frame. Use the edge of the vise as to position the fixture when the part is exchanged, or mount a stop.
Next flip the fixture upright, as shown below. Square it up and clamp it. The nice part about this setup is that the screws are accessible and the part can be switched without removing the fixture from the vise.
Next, flip the part over and clamp it in the vise as shown below. I used a small stop on the vise and used a machine square before clamping. A larger, already square, stop would be better.
Finally mount the fixture with the brake hanger up and drill the hole for the brake hanger, and then the equalizer beam. Drill the first equalizer beam hole all the way through the fixture.
With the help of Matthew Kobel and Gordon Carlson (see his work on http://www.locogear.com/page15.html).