Amongst the various purposes to which it is possible to apply the
lathe, may be noticed the drilling out grooves and mortises, a method
used in some of our Government arsenals, for cutting the recesses
for the reception of the Venetian lath work in cabin doors. The same
method is, of course, applicable to numberless similar cases, although
designed for the special object named. The apparatus is shown complete
in the drawing, Fig. 272, and the component parts in the succeeding
diagrams. A is a kind of compound slide rest, or vertical straight
line chuck, having a movement in a direction parallel with the lathe
bed at F; while the circular plate being pinned through its centre
to a slide, H, can be moved up and down by means of the handle G.
This circular plate can be set in any position, and has a projecting
shelf or rest to carry the work, which is steadied by guide pins, as
will presently be explained. The part F, has a bed similar to that
of an ordinary slide rest, which is clamped to the lathe bed by a
bolt and nut, as usual. This carries likewise chamfered bars, between
which slides the horizontal plate to which the vertical part of the
apparatus is attached. This is first a plate with chamfered edges,
Fig. 273 A, and a second similar but rather wider plate, Fig. 274 B, with
guide bars, likewise chamfered, to slide upon A. From the front of B
rises a stout pin, on which the circular plate, C, turns, which can
be clamped by a central nut, or otherwise, as in an ordinary compound
slide rest. This nut should not project above the general level of the
plate. On the face of the latter is, as previously stated, a rest, or
narrow metal shelf, D, and pins, _e_, _f_. The plate may be variously
arranged in this respect by substituting any kind of holdfast or
guide, according to the work desired to be done by its aid. The upper
slide is depressed by a hand lever acting on a pin fixed in the
sliding plate, Fig. 275; or, if preferred, by a similar lever, with a
quadrant and chain, or rack movement. The horizontal slide is worked
by means of a stirrup for the foot, with cord attached, acting on a
bell-cranked lever, seen in the first figure. To cut the grooves in
a bar, for Venetian blinds--as described--the lath to be drilled is
attached to a flat strip of thin iron, drilled with holes, Fig. 276 A,
as wide apart as the required distance between the grooves. It is then
laid against the shelf, and the guide pins are made to enter the holes
in the iron. The clamping nut of the round plate is loosened, until
the bar is set to such an angle that the grooves to be cut will form
vertical lines, Fig. 276. It is then clamped securely.
[Illustration: FIG. 272.]
[Illustration: FIG. 274.]
[Illustration: FIG. 275.]
[Illustration: FIG. 273.]
[Illustration: FIG. 276.]
It is necessary to be able to adjust the piece to be cut, as regards
its height, above the lathe bed. This is effected in part by the
position of the movable shelf--fixed by pins--and partly by guide or
set screws, which regulate the traverse of the slides. Suppose the bar
adjusted as in Fig. 276, the groove to be cut being brought opposite
to the drill. The set screws--two of which are seen at _x, x_, Fig.
275--acting on the handle, regulate the precise length of each groove.
A similar stop, connected with the horizontal part of the machine,
regulates the advance of the wood towards the drill, and thus the
depth of the cut. Hence it is only necessary to set these carefully
at starting--the pins on the guide plate insuring the proper width
between the grooves--and the lathe being put in motion, any number of
precisely similar grooves can be drilled with the utmost rapidity and
neatness.
An inspection of the drawings will show what numberless purposes may
be served by this simple apparatus, which may be modified in its
details, while its principle of action is maintained. The drill should
have a chisel and be kept to a keen edge. The lathe should be put in
rapid motion, and if the required cut is to be deep, it should be cut
at twice. The lower slide should return to its place by means of a
spring when the foot is raised, the vertical slide being movable in
both directions by means of the slotted part of the handle.
NOTE.--The above being taken from an apparatus for a
steam lathe, the stirrup action maybe used, as the foot is at
liberty. A foot lathe would require a slight modification. In
Fig. 275, the depressing handle is shown as if the chamfered
bars were fixed to the sole plate, and the plate A, were
movable, as is sometimes the case. When made according to the
above description, the handle would, of course, be pinned to
the fixed vertical plate, A, to which also the stops would be
attached, and the pin which passes through the slot of the
handle, must project from one of the chamfered bars. Either
plan may be followed, but the pattern described is calculated
for a stronger apparatus; inasmuch as the vertical plate can be
secured more firmly to the chamfered horizontal slide than the
mere pair of guide bars--the two might, in fact, be made in one
casting, if preferred.