Millers Falls No.2 Eggbeater Drill Type Study
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Frame and Gear Changes from Type M to Type L

Type M (the older design) is at left, Type L at right. The frame of Type L has thicker members, but the layout is basically the same, as though the framne was simply beefed up to increase the individual members' resistances to bending. The spindle bearing housing of Type M was tapered, whereas Type L has a cylindrical shape, making it easier to grasp Type L in a bench mount as a drill press. The end thrust of the chuck spindle is taken by a female cone center in Type M and by a single hardened steel ball in Type L. The main gear of Type M has the same number of teeth as that of Type L, but the faces of the teeth are wider in M than in L. This is more a matter of mis-match between the widths than it is of conscious design, because the pinions are both the same width. However, there was an advance in the utilization of the gears. Type M has a sixteen tooth pinion and a seventy-eight tooth gear, which makes a ratio that is divisible by two. Type L's pinion has seventeen teeth, which is a prime number, so individual pairs of teeth in the mating gears do not revisit each other as often in Type L as in Type M, which makes the teeth wear much more evenly. This is a fine point in a device which receives minimal care, but it does represent progressive design considerations. Finally, the hub of the main gear of Type M has more of a finished, one-off look than does Type L, because its outer diameter has been machined, whereas Type L's gear hub has been left as a raw casting there. Not seen in this picture, the outer face of Type M's gear has been machined smooth over the whole width of the toothed rim, whereas Type L's gear has a decorative rim, partly machined and partly left rough, but from a more refined casting pattern. The Type Pre-L shares the main gear of the Type M but its pinion has seventeen teeth like the Type L, and so the Type Pre-L represents an intermediate stage between the Types M and L. Further, the frame of the Type Pre-L is heftier than the Type M and more closely resembles the Type L.