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 ISO revolutions per minute, drives a 

 countershaft with a 12-inch pulley. AVliat 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 imllej. 



3. "\Aniat will be the diameter of a pulley making 180 r. p. m. to 

 drive a 12-inch pulley 450 r. p. m. ? 450 Xl2-f-180= 30-inch pulley. 



SAW GAUGE. 



Stubs's standard English gauge is in general use by saw manufac- 

 turers in this country. 



No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No. 

 No, 

 No. 

 No. 

 No. 

 No, 



No. of wire gauge. 



Fractional equivalents. 



•^ inch scant . 

 1^ inch full . . . 

 a inch scant . 

 ^ inch full . . . 

 ^ inch full . . . 

 |-| inch scant . 

 J4 inch full . - - 

 j4 inch scant . 

 •^ inch full . . . 

 /j inch scant . 

 J- inch scant . . 

 ■^ inch scant . 

 ■^ inch full . - . 

 ^ inch full . . - 



•^ scant 



•jJj inch full... 

 T»j inch scant . 

 •^ inch full... 



Decimal 



eq uiva- 



lent. 



Incli . 

 .300 

 .284 

 .259 

 .238 

 .220 

 .203 

 .180 

 .165 

 .148 

 .134 

 .120 

 .109 

 .095 

 .083 

 .072 

 .065 

 .0.58 

 .049 



MILL-MACHINERY TERMS. 



Bar-k (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. 



