METAL WORKING MACHINERY 287 



to the credit of the last fifteen years, the hammer alone hav- 

 ing been in use prior to 1890. 



The great expansion in the use of power presses which has 

 recently taken place must be credited largely to the growth 

 of the electrical industries. The advent of the laminated 

 armature for electric generators and motors called for accu- 

 rately made punchings of sheet metal of a size and in numbers 

 previously unknown. The power press furnished the natural 

 method of making them, and in its development the capabili- 

 ties of the machines were demonstrated as they had never 

 been before. 



The electric motor as a means of driving machine tools 

 was first seriously proposed about ten years ago, and was gen- 

 erally looked upon by mechanical men as a fad of the elec- 

 trician. The innovation nevertheless obtained a foothold, 

 and advantages which were not foreseen were found to attend 

 it. It has Ijecome the accepted method of driving factories 

 which are composed of many departments, the flexibility and 

 economy of the system in distributing power over a consider- 

 able area from a central station being here the factor of domi- 

 nating importance, and those which are of a nature requiring 

 tools and machines to be located at considerable distances 

 apart, especially if they are also to be intermittently operated. 

 It is also making rapid progress in machine shops, to which the 

 above limitations do not apply, though in such applications 

 opinion regarding its merit is still unsettled. A leading con- 

 troversial point is the attachment of individual motors to each 

 machine tool versus group driving of several machmes through 

 a smgle motor and a line shaft. There are well defined con- 

 ditions under which each method is suitable, but there is still 

 a wide intervening field of del:)atable ground. As a matter of 

 fact, in this field the individual motor is making rapid progress 

 — more so perhaps than can be readily explained. 



Like the increased development of power presses, the 

 floor plate portable tool system of attacking heav^^ work must 

 be credited to the electrical industries, which in this instance, 

 curiously enough, furnished both the work for which the sys- 

 tem was first devised and the means for doing the work. It 

 was the machining of the ring or magnet frames of large electric 



