First, ascertain by Rule 1 the pitch diameter for a wheel of 1-inch pitch, and the given number of teeth.
Second, divide given pitch diameter by the pitch diameter for 1-inch pitch.
The quotient is the pitch desired.
Example.—What is the pitch of a wheel with 148 teeth, the pitch diameter being 72′′?
First, pitch diameter for 148 teeth, 1-inch pitch, is—
| 8 | teeth | 2.54 | 65 | ||
| 40 | „ | 12.73 | 2 | ||
| 100 | „ | 31.83 | |||
| 148 | „ | 47.10 | 85 | ||
| Second, | 72 | = 1.53 inch equal to the pitch. | |||
| 47.1 | |||||
This is nearly 11⁄2-inch pitch, and if possible the diameter would be reduced or the number of teeth increased so as to make the wheel exactly 11⁄2-inch pitch.
Rule 3.—Given —— pitch and pitch diameter; to find —— number of teeth.
First, ascertain from table the pitch diameter for 1 tooth of the given pitch.
Second, divide the given pitch diameter by the value found in table.