IMPROVEMENTS IN RIFLING MACHINES
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by George Innes at the Office of
the Commissioners of Patents, with his Petition, on the 19th
September 1868.
I, GEORGE INNES, of Woodpecker Road, New Cross, in the County
of Kent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN RIFLING MACHINES," to be as follows:-
My Invention relates to machinery for forming the spiral grooves
or channels in the bore of rifled ordnance or fire-arms, and the said
Invention consists chiefly in the means whereby the spiral grooves may
be cut to any desired pitch or number of turns in a given length. To
form such spiral grooves or channels in the bore of a gun two motions
are necessary, one in a longitudinal direction in line with the bore
of the gun, and the other transversely to the bore, the pitch or twist
depending upon the relative speed of the two motions.
One method heretofore employed of producing the rifling is to connect
the rifling tool or cutter with a bar upon which is formed a spiral thread
corresponding in pitch with that to be formed in the gun, the said
bar being passed endwise through a nut which causes its rotation. This
method however, though simple in principle, is objectionable in practice,

page_text: as to produce the slightest variation in the pitch of the rifling a new
bar and nut must be provided. The cost and delay incurred by this
method of rifling has led to attempts to construct machines by which
the rifling could be produced with any desired pitch or twist. In such
machines the gun is fixed upon a horizontal bed whereon is fitted a
travelling carriage which carries the rifling head or tool. The carriage
is caused by a screw or other means to advance upon the bed, and the
tool at the same time is slowly turned on its axis through a rack and
pinion operated by an oblique bar arranged at the side of the machine
bed, the pitch or twist of the rifling being varied by changing the angle
of the said.bar in relation to the bed. These machines however, though
found to act well within certain limits, are yet very imperfect, as the
variation in the pitch obtained by the use of the inclined or oblique bar
is very limited, and the said bar being inclined horizontally from the bed
of the machine necessarily occupies a great deal of room.
By my improvements these objections are entirely obviated. I
construct the bed of my machine similar to an ordinary lathe bed,
or I can use a lathe bed by simply removing the heads from the same.
Upon this bed I fit a saddle or carriage and connect the same by a
suitable nut to a screw extending from end to end of the bed. Parallel
with this screw and preferably outside the bed I arrange a toothed rack,
into which is geared a pinion fixed on a short transverse screw spindle
which is supported in suitable bearings on the travelling carriage or
saddle. The latter also carries a rack which is fitted to work in a guide-
way extending across the top of the saddle just above the transverse
spindle or shaft. This rack is connected by a nut with the transverse
screw, and gears into a pinion on the thrust bar to which the tool bar is
fixed, which bar is thereby caused to rotate as the carriage or saddle
moves along the bed. The pitch or twist of the rifling is varied by
changing the relative speed of the carriage and thrust bar, and I prefer
to make these variations by changing the pinions on the said bar, though
the same object may be effected by changing other parts of the gearing.
The guideway of this rack is supported upon brackets secured to the top
of the carriage or saddle, the said brackets being formed with vertical
apertures or slots through which screws or bolts are passed into feet or
flanges on the guideway. These slots allow the said guideway to be
raised or lowered to adjust the rack properly in gear with the various
sized wheels or pinions which may be used. To facilitate this adjustment
the nut on the tranverse screw is held in a yoke attached to the rack, the

page_text: said yoke being fitted to slide over the sides of the nut and hold the same
securely without disconnecting it from the rack when the same is either
raised or lowered. Each of the rack pinions is preferably made in two
parts, each part forming a thin wheel, and the two parts being secured
together, with the teeth of one part slightly in advance of the teeth on
the other part to prevent "back lash." The thrust bar is preferably
supported in a bearing having a series of grooves or shoulders which fit
similar grooves and shoulders on the bar. The gun or cannon to be
rifled is firmly secured in any ordinary and convenient manner upon the
bed of the machine in line with the centre or axis of the rifling bar,
which is fitted with tools or cutters of any suitable construction. The
cutters are then introduced into the gun. The desired pitch of the
rifling having been ascertained, and the gearing properly adjusted to
produce the same, motion is imparted to the main screw of the machine
preferably in the proper direction to cause the carriage to move away
from the gun, the rifling head or tool being thus drawn from the breech
of the gun to the muzzle. As the said carriage advances the longitudinal
rack through the pinion turns the transverse screw shaft, which by means
of the nut moves the transverse rack across the carriage, and thereby
causes the rotation of the thrust bar and rifling head.
In rifling shunt guns or guns with a variable twist in the grooving,
I employ a bar fixed on the side of the bed parallel to the same, and
having in the proper place either projections or depressions, which act on
the transverse spindle and thereby operate the rack to give the required
motion to the thrust bar and rifling head.