CHAPTER XVII 



ROPE, WIRE, AND BELTING 



247. Wire. AVire is made from a steel or iron rod by pulling it 

 through a hole, or die, of smaller diameter than the n>d. Tl 

 called drawing, and is done while tin- metal is cold. It is known as 

 wet drawing when the metal is luhricated. and as dry drawing when 

 no lubricant is used. The drawings an- made with a smaller sized die 

 each time, until the desired diameter of wire is obtained. Cold draw- 

 ing of steel and iron raises the elastic limit and ultimate strength of 

 the metal and decreases its ductility. It is made ductile a^ain ^y 

 annealing, and is finished by giving it the proper temper eonsi>tent 

 with the de>ired use. 



The Mining J<>nrnl for 1896 gives the following values fur the 

 strength of wire. 



lb./in. Hi., 



Ir..n \viiv 80,000 lli-!i-r:ii-li..n >!<] \\in- . . 180,000 



\viiv . . . 00,000 Crucible cast steel . . . 240,000 

 Mild open-hrarth steel wire 130,000 



Piano wire varies in strength from 300,00011-. in. ' to 4(Mi.ii(in 11,. 



248. Wire rope. Wire rope is made by twi>ting a numU*r <>f steel 

 or iron wires into a strand, and then t\vi>tin^ a number of t 



st lands about one of the strands, or about a hem],, 

 manila, jute, or cotton strand. The exact compsiti<>n 

 of the cable or wire rope will depend upon the s 

 for whieh it is designed. The hemp core gives added 

 pliahilitv to the cable, and acts as a means of lubricat- 



;. 1C.7 



in^ the strands and wires; this reduces the internal 

 friction in the cable, and adds mueh to its life in case it is used \\ 

 I'liahility is required, as in running over sheaves. Fii:. 1 '7 is an illus- 

 tration of the cross section of a cable in which the separate strands 

 each have a hemp core. Such a cable can be used where g 

 pliability is required. Fig. 168 shows a cross section of a cable witli 



