[Doug G]

Ahhh... fond memories of our early years of putting those bolt hole circles into sprockets that fit those skyway wheel hubs. The way we did it was to CAD a pattern of the bolt hole circle with center point marks for each hole and a center hole. Print out a 1:1 scale drawing, cut it out, glue it on the sprocket centered with the middle of the sprocket (hardest part), use a punch for the holes to be drilled lined up with the center points on the drawing, and drill away!!

On second thought if you use a lathe to scribe the hole circle and then an edge to scribe some lines that bisect the circle into the parts where you want holes, that may be just as easy.