I fabricated a gear cutting machine from a 300:1 gear motor and used a 2-1/2" thrust bearing to bolt the gears down to a  X, Y table.  The table is used to feed the gear while cutting the gear blanks, .  The azimuth bearing is 333 teeth, I used a 1/2"-13 tap as the cutting tool.  The bottom picture is the altitude bearing, the blank is the scrap core from the upper ring and had a hole in it that was used for the main component of the mirror cell,  I made a plywood adapter to hold the ring while machining.  The gear has 655 teeth, I am only going to use a section of the final product for the scope.   Top right is the  is the finished azimuth bearing, only the lightning holes have to be bored.