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Step Cut Sphere 288a-96 by Bob Keller

Step Cut Sphere 288a-96 designed by Bob Keller 11-99
288 facets 96 index
L/W = 1.000 H/W = 1.000 Vol./W^3 = 0.509
Hemisphere A
p 90.00 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Cut to equal depth, set size
1 82.56 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match p, cut level girdle (equator) line
2 67.67 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 1
3 52.74 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 2
4 37.74 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 3
5 22.67 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 4
6 7.56 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 5, meet apex (pole)
Hemisphere B
1 82.56 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match equator
2 67.67 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 1
3 52.74 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 2
4 37.74 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 3
5 22.67 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 4
6 7.56 02-06-10-14-18-22-26-30-34-38-42-46
50-54-58-62-66-70-74-78-82-86-90-94
Match 5, meet apex (pole)

Step Cut Sphere 288a-96 Cutting Notes

The Step Cut Sphere 288a-96 Design File is available for GemCad users.

This step cut design for a sphere yields a "true" sphere. All of the vertices are equidistant from its center when the step cut courses are properly spaced. The length of each facet edge lying on the meridian lines forming 12 great circles running through the poles should be made equal to the length of the facet edges lying on the 13th great circle at the equator. In other words, the length of each facet edge lying on the 13 great circles described by the meridians and the equator are all equal. Make yourself a simple gage by marking or cutting a piece of index card that matches the edge length of the equator facets after you have cut the "1" course facets on the first hemisphere, which establish the equator.

Begin by cutting a 24-sided cylindrical preform. The height of the preformed cylinder must be equal to or greater than its maximum width for you to have enough material when you get to the course 6 (pole) facets. When you cut the course 1 facets for the first hemisphere, create a level 'girdle' (equator) line at half the height of cylinder.

Transfer when you've finished the first hemisphere, and repeat the course 1-6 sequence on the second hemisphere.

If you cut a Step Cut Sphere 288a-96 of your own, be sure and let me know what you've cut and how you made out.

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