On 1/3/2011 2:30 PM, Jim Wilkins wrote:
On Jan 2, 6:55 pm, wrote:
...
I just went down and double checked. Twenty revolutions of the crank
gives one revolution of the table. Perhaps it was a compromise in
cranking speed; the table has no way to decouple the worm gear and shift
the table by hand. It is a horizontal only table similar in appearance
to the No. 86 made in the fifties. The age is unknown- it was a Cabin
Fever purchase.

Kevin Gallimore

To make N divisions on the table you turn the crank 20/N times

table crank
2 10
3 20/3 = 6 full + 66.7/100
4 5
5 4
6 20/6 = 3 full + 33.3/100
8 20/8 = 2 full + 50/100
and so on.

To mill a hexagon, like a bolt head, you'd start at zero and cut a
flat. Turn the crank twice plus 33.3 marks and mill the second flat.
Turn two full revs and stop at 66.6 for the third. Next turn two full
revs and advance to zero (=100) for the fourth, etc.

I wrote a spreadsheet that lists all the full and partial turns for up
to N = 100 for my 40:1 table.

jsw


Good idea. I'll make one up and post it on the door of the cabinet that
holds the table.

Thanks,

Kevin