Martin; Try to find the axis with the most amount of play. This is usually the X axis. Work only in one direction in that axis. You can slightly tighten the table lock while moving to the next co-ordinate to keep the lead screw loaded. Use the Y axis as the one you will have to backtrack with. Do all the holes you can in one direction first.
I.E. All the co-ordinates that are plus from your original datum. Keep the cross slide lock slightly tightened to keep the Y axis lead screw loaded. Return to your Y axis datum, and go slightly past it. Then move the X axis to the next co-ordinate and repeat the process.
So to try and make this explanation simpler, let's use Rick's gear as an example. And let's say the bolt circle is 1 inch. That makes the radius from the axle hole to each of the drilled holes .500 inch. Movements from right to left of the table (X axis) will be +, and movements of the table from front to back (Y axis) will be +. The axle hole will be the datum, X = 0, Y = 0. Pick up the center of the axle hole with an indicator, and lock the table locks. Turn the handle for the table clockwise until the play is out, and set the dial for "0". Turn the handle for the cross slide clockwise until the play is out, and set that dial for "0". Loosen the table lock for the cross slide. Move the table in the Y axis, (cross slide) to .500 on the dial. (this will be 2 and 1/2 turns clockwise, and will actually read .100 on the dial) Lock the table locks and drill the hole. ( this should be the one nearest to you) Unlock the cross slide lock, and back the Y axis to - .500 ( 5 turns counter clockwise), and go a little past that mark. ( half turn will do) Now turn the Y axis handle (cross slide) clockwise to the .100 mark. and lock the table. Drill that hole. ( it will be the one farthest from you) Now you have to move to the first of the holes at 45 degrees off the axle hole. Since the sine for 45 degrees is .70711, we multiply .500 times .70711 to get .3535. Turn the X axis handle 1 and 1/2 turns clockwise. The dial should read .100. Now go past that to the .135 mark, which should be .353 from the axle hole in the X axis. Move the Y axis handle to - . 353. ( 2 turns counter clockwise to 0 on the dial, then lightly lock the cross slide lock and turn the handle to .146 on the dial.) Lock the table and drill this hole. (this will be the hole to the right of the axle hole, and farthest from you) Now, unlock the Y axis cross slide and simply go to + .353. ( 3 1/2 turns clockwise on the handle and past 0 to the .153 on the dial. You should be 1 and 1/2 turns past the "0" datum of the Y axis [plus .053]) Drill the hole. ( this should be the hole to the right of the axle hole and nearest to you) Now unlock the cross slide and back the Y axis to 0 (4 turns counter clockwise of the handle) Lightly tighten the cross slide lock, and turn the handle clockwise to "0". Turn the X axis handle clockwise to 0 on the dial, and another half turn to .100. Lock the table and drill the hole. This should be the hole farthest to the right, and completes the hole pattern to the right of the axle hole. Now unlock the X axis table lock, and turn the X axis handle counter clockwise 5 turns, plus a little. (half turn will do). Snug up the X axis table lock a little, a turn the handle clockwise to the .100 mark on the dial. This should be - .500. Lock the table and drill the hole. This will be the hole farthest to the left. Unlock the X axis table lock, and turn the handle half a turn, then to the .046. Lock the table. Unlock the Y axis cross slide lock and turn the Y axis handle counter clockwise 2 turns, then clockwise to the .046. Lock the cross slide and drill the hole. This will be the hole to the left of the axle hole and farthest away from you. Now unlock the cross slide lock and turn the Y axis handle clockwise 3 turns and to the .153 on the dial. Lock the table and drill the hole. This will be the hole to the left of the axle hole and nearest to you. That finishes the drilling.
Naturally, this is much simpler with a DRO (digital read out) But if you have neither a DRO nor rotary table with degree scale it is the most accurate. And really should be done with a center drill to spot the holes in any event.
