12
15
60
12
300 ) 180.0 ( 0.6
1800

Then add the 1 to the .6 = 1.6, and this divided into 192 = 120.

By continuing this process for each of the 16 cutters we obtain the following table:—

Number of
Cutter.		Number of
Teeth.		Number of
Cutter.		Number of
Teeth.
1 12 9 26
*2 13 *10 30
3 14 11 35
*4 15 *12 42
5 17 13 54
*6 18 *14 75
7 20.6115 120
*8 23 *16 300

Suppose now we take for our 8 cutters those marked by an asterisk, and use cutter 2 for all wheels having either 12, 13, or 14 teeth, then the next cutter would be that numbered 4, cutting 14, 15, or 16 toothed wheels, and so on.

A similar table in which 8 cutters are required, but 16 are used in the calculation, the largest wheel having 200 teeth in the set, is given below.

Number of
Cutter.		Number of
Teeth.		Number of
Cutter.		Number of
Teeth.
1 12.79 26.5
2 13.510 29
3 14.511 35
4 15.612 40.6
5 16.913 52.9
6 18 14 67.6
7 21 15 101
8 23.516 200

To assist in the selections as to what wheels in a given set the determined number of cutters should be made correct for, so as to obtain the least limit of error, Professor Willis has calculated the following table, by means of which cutters may be selected that will give the same difference of form between any two consecutive numbers, and this table he terms the table of equidistant value of cutters.

TABLE OF EQUIDISTANT VALUE OF CUTTERS.

Number of Teeth.
Rack—300, 150, 100, 76, 60, 50, 43, 38, 34, 30, 27, 25, 23, 21, 20, 19, 17, 16, 15, 14, 13, 12.