. American engineer and railroad journal . *iQ 2% \M> 3-FOOT BICKFOBU RADIAL DRILL. The speed box in connectionwith the back gears on the headfurnishes the machine twelvechanges of speed, the range andgradations of which are shownin Table 1. A comparison of the figuresin the first three columns indi-cates that the manufacturershave exercised great care in theselection of the gears, as in noinstances does the cutting speedvarj from the theoretical oneby more than .84 of a foot perm
. American engineer and railroad journal . *iQ 2% \M> 3-FOOT BICKFOBU RADIAL DRILL. The speed box in connectionwith the back gears on the headfurnishes the machine twelvechanges of speed, the range andgradations of which are shownin Table 1. A comparison of the figuresin the first three columns indi-cates that the manufacturershave exercised great care in theselection of the gears, as in noinstances does the cutting speedvarj from the theoretical oneby more than .84 of a foot perminute. An interesting fact, which isvery nicely illustrated in Table2, which was furnished us bythe manufacturer, is that speedswhich aic in true geometricalprogression are not by anymeans the besl ones to beused on a machine tool of thiskind An inspection shows thai in-stead of giving a series ofcutting speeds, as shown inTable No. 1, in which no speedis more than .84 of a foot toohigh, nor .78 of a foot too low;the cutting speeds in thegeometrical series vary too high to .92 of a foot toolow; in one case the maximumerror is but per cent
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
