• Take all but one of the disks, and cut circular hole in each, 360mm diameter to
form rings (see diagram 14).
14. RINGS
360
• Draw a circle 360 mm diameter on the remaining disk
• Drill a 12 mm hole at the centre of this disk, to help with centring.
• Glue the rings on top of the remaining disk, to form a stack, with a hole 60mm
deep (diagram 15). Use plenty of glue at the insides of the rings.
• Cut out a small disk of 15 mm plywood, 140 mm in diameter, and drill a 12 mm
hole at its centre.
• Placing a 12 mm bolt through both holes, glue the small disk into the exact centre
of the hollow. Use plenty of glue at the edge of the disk.
15. STACK
60 DEEP
140
• Mount another piece of wood or board onto a lathe, a motor or the wheel hub of a
small vehicle (for example a 3-wheel taxi). This is a the faceplate (see diagram
16).
• Spin the faceplate and use a pencil to make a very small circle at the centre.
• Drill a 12mm hole precisely at this centre. Hold the drill parallel to the shaft.
• Screw the glued stack onto the faceplate, using a 12mm bolt to centre it. Use four
woodscrews through the disk and into the faceplate.
• Check that the face of the mould runs true. You can do this by holding a pencil
close to it while it spins. Where the pencil makes marks, the face is 'high'.
Loosen the screws and insert pieces of paper between the faceplate and the stack,
on the opposite side from the pencil marks. Tighten the screws and check again.
PMG manual
page 16
June 2001