62 
BULLETIN 718, U. S. DEPARTMENT OF AGRICULTURE. 
and the pitch diameter is 4 inches, the diametral pitch is 10, or, 
properly speaking, the gear is 10 diametral pitch. Circular pitch is 
the distance from the center of one tooth to the center of the next 
tooth measured along the pitch circle. If this distance is one-half 
inch, the gear is said to be one-half circular pitch. 
CALCULATING THE SPEED OF SAWS, PULLEYS, AND DRUMS. 
EXAMPLES. 
1. A 30-inch pulley, making 180 revolutions per minute, drives a 
countershaft with a 12-inch pulley. What is the speed of the smaller 
pulley? 180X30-^-12=450 r. p. m. 
2. A countershaft is to make 450 r. p. m., driven by a 30-inch pul- 
ley making 180 r. p. m. What will be the diameter of the counter- 
shaft pulley? 180X30^450= 12-inch pulley. 
3. What will be the diameter of a pulley making 180 r. p. m. to 
drive a 12-inch pulley 450 r. p. m. ? 450Xl2-^-180=30-inch pulley. 
SAW GAUGE. 
Stubs's standard English gauge is in general use by saw manufac- 
turers in this country. 
No. of wire gauge. 
Fractional equivalents. 
Decimal 
eq uiva- 
lent. 
No.l 
•& inch scant 
Inch. 
.300 
No. 2 
-fo inch full 
.284 
No. 3 
.259 
No. 4 .; 
H inch full 
.238 
No. 5 
sV inch full 
.220 
No. 6 
.203 
No. 7 
H iuch full 
-180 
No. 8 
^ inch scant 
.165 
No. 9 
^ inch full 
.148 
No. 10 
.134 
No. 11 _ 
.120 
No. 12 
.109 
No. 13 
.095 
No. 14 
.083 
No. 15 
.072 
No. 16 
^ inch full 
.065 
No. 17 
.058 
No. 18 . 
.049 
MILL-MACHINERY TERMS. 
Back (of a saw tooth) — The upper or convex part of a saw tooth. The lower 
or concave portion is called the face. 
Bit — A tooth used in an inserted tooth saw. The knives used on the cutter 
heads of surfacing machines to cut a tongue and groove. 
Board mill — One that makes a specialty of 1-inch and 2-inch lumber as com- 
pared to a timber mill which cuts lumber of greater thickness. 
Bumper — A device placed at each end of the carriage run to absorb the shock. 
It is usually a piston fitted with a cylinder which contains live steam or air, 
buffer. 
