NOTES:
 100x100 nominal. 3.175mm bit, 13.3mm material
  Inside: 96.7 x 96.7
  Outside: 123.3 x 123.3

Golden Ratio: 1.61803398875

Biggest: 

Nominal: 21" x 13" x 8"  <- 
	3/4" Plywood (18.5mm) (Assume 20mm ov.)
	6.35mm bit.
 **   650mm x 401.72mm x 248.277mm
    ID:643.65mm x 395.37mm x 241.93mm

Next: (-3mm edges)
	3/4" Plywood (18.5mm) (Assume 20mm ov.)
    6.35mm bit.
    OD: 392.37 x 238.93 x 149.872
 **     361.72 x 208.28 x 119.222  NOMINAL
    ID: 355.37 x 201.93 x 112.872

Next: (-3mm edges)
  13.3 mm thick MDF. 6.35mm bit
	OD: 198.93 x 109.872 x 75.99
        178.68 x 89.622 x 55.74
    ID: 172.33 x 83.272 x 49.39

Next: (-2mm edges)
   4.6mm thick strangeboard.
   1/8" bit (3.175mm)
    OD: 81.272 x 47.39 x 31.04
  **    75.247 x 41.365 x 25.015
    ID: 72.072 x 38.19 x 21.84