M_V's multitude of bikes and adventures in the land of framebuilding

For the handlebar clamp I went with a similar technique as you would when building a frame out a vice and doing the seat-tube, zero the level across the vice, check the extension tube is at 90deg to that, tack, check, adjust, braze.

Think I also put the handlebar clamp in one end of the vice and checked the extension tube was parallel to the jaws.

For the extension tube/steerer clamp, I had built a jig out of extrusion and ali bar but I found brazing the stem in the jig wasn't working, the ali bar I was using to replicate the steerer acted like a big heatsink so I couldn't get enough heat into that tube yet the extension tube was getting overheated. The jig did at least let me verify the mitre was right and to braze it I think I opened the vice right up and put it length ways in there and used a digital angle finder to check that the handlebar clamp and the end of the steerer clamp (which I squared off in the lathe so knew it was square to the tube) were at the same angle.

I tacked it like that and then the steerer clamp tubing happens to be 32mm od and I have about another 500mm of it so I clamped the stem to that, put that in a tube block and clamped that in the vice.

So as far I can tell I think it should all be pretty square, we'll see what its like once its on a fork and has a 750mm wide handlebar in it though...