Better explain that a bit more.
I have a scrap ball, and I've sawed off the flange to use it as a drill jig, so far thats clear.
But instead of just clamping the flange on the axle and bashing the holes, I'm gonna use a mill to drill 4 new holes exactly 13 degrees, 2 holes clockwise for the nearside and 2 anticlockwise for the offside, this way I bolt on the drill jig using the new holes and bash through with the drill.
This leaves all the accurate work to the mill where it belongs, I just need to bash with a drill on the drive, or more likely clamp the casing in mi pillar drill.
Probably wont need to weld up the holes, and I wouldnt want to do that for various reasons, I might warp the flange, and I'd have to grind the surface flat which would probably start a leak, if I block the holes I'll screw in some allthread which is mild steel so the drill wont wander, and then weld the stud at the backside only.