. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. THE HALF-TONE PROCESS. Where the luxury of a separate electric motor for eachmachine can be afforded all countershafting is dis-pensed with, and the machines can be placed anywherethat suits best. The power for driving machinery is invariably theelectric motor, unless power shafting is already running in the then it isgenerally an ad-vantage to havea motor, as thisrenders thephoto- engravingdepartment in-dependent, andable to run whenthe rest of theestablishmentis shut
. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. THE HALF-TONE PROCESS. Where the luxury of a separate electric motor for eachmachine can be afforded all countershafting is dis-pensed with, and the machines can be placed anywherethat suits best. The power for driving machinery is invariably theelectric motor, unless power shafting is already running in the then it isgenerally an ad-vantage to havea motor, as thisrenders thephoto- engravingdepartment in-dependent, andable to run whenthe rest of theestablishmentis shut 2 to3 will run allthe machineslikely to be re-quired in a photo-engraving estab- Fig. ioo. lishment, and each separate machine can be run by a motor of from\ to I It is becoming quite a commonpractice now to have an independent motor for THE MOUNTING AND PROOFING. Continuous current motors are the most satisfactorywherever this current can be obtained, as they willstand a temporary overload better than alternatingcurrent motors. All the machines being run at a comparatively highspeed, the shafting should be light and free running,with good lubrication, well-balanced pulleys, and veryflexible belting with neatly-made joints. The most important machine is the router, the pur-pose of which is to rout or hollow out portions of theplate which are to be left white in the finished is requisite in vignetted and shaped blocks, andespecially in blocks for catalogue illustration. The router (fig. 100) is made in a variety of forms,but one principle is common to all, viz., that a drill-likecutter is revolved at a high rate of speed whilst in con-tact with the plates, cutting out the metal in circlesrunning one into the other as the cutter or the work ismoved about. The machines may be divided into twoclasses : (a) thos
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