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.