Original fork blades were tapered and curved.
I use oval tubing 30 x 16mm. Basically its a ERW 1" tube that's been formed in oval dies.
The tube needs a taper towards the drop out. I cut out a long 'wedge' and then carefully squeeze the tubes together in the vice and hold them in that position with jubilee clips. Once I'm happy I tig tack along the length and remove the jubilee clips. The complete length is then tig welded together.
The blades are then curved using heat and the former.
I find that to form the curve once the blades are tapered and welded is better than curving them before welding.
I next drill the axle hole in the drop outs on the mill.
The blades are then set in the spacer brackets and I machine the slots for the drop outs on the milling table.
The drop outs are then welded into the blades, again using the spacer brackets and a dummy axle running through them.
I then cap the top of the blades by shaping a piece of 2mm plate and braizing them in position. I drill a small vent hole at the bottom of the blade, which allows the blade to vent whilst braizing. This can be filled in afterwards.
The blades are then put to one side, while I fabricate the fork stem.
I use 30mm tube with a 5mm wall.
The tube is cut to length and the top is threaded 1 1/8" x 26 tpi.