AN IMPROVED METHOD OF RIFLING THE BARRELS OF FIRE-ARMS AND CANNON, AND APparatus THEREFOR
Year: 1871

page_text: PROVISIONAL SPECIFICATION left by Thomas James Smith at the
Office of the Commissioners of Patents, with his Petition, on the
29th November 1871.-A communication from abroad by François
Alexandre Le Mat, of 23, Boulevard de Strasbourg, Paris, France.
I, THOMAS JAMES SMITH, of the Firm of Robertson, Brooman, and
Company, of 166, Fleet Street, in the City of London, Patent Agents, do
hereby declare the nature of the said Invention for "AN IMPROVED
METHOD OF RIFLING THE BARRELS OF FIRE-ARMS AND CANNON, AND APparatus
THEREFOR," to be as follows:-
In the ordinary processes of rifling barrels the grooves are produced by
removing the metal by means of tools or cutters actuated by special
machines, which results in a solution of continuity of the metal and
other inconveniences. The mode of operation is long, costly, and
difficult; the grooves produced are irregular and their interior surface is
striated and broken in consequence of the gripping action of the tool

page_text: which bites the metal. But the greatest defect is the alteration of the
material which takes place in those parts acted upon by the cutting
tools, whereby its molecular condition is changed at the surface of the
bore at the expense of the resisting power of the barrel and the
durability of the grooving.
All these inconveniences are avoided by this Invention, which consists
in forming the grooves of a barrel by the aid of a moulding mandril
introduced by force into the barrel, while the latter is softened by heat
to which a rotating forwards movement is imparted.
This mandril which is of hard steel has formed in relief upon it ribs
from which the grooves are to be moulded or formed in the barrel by the
compression or repulsion of the metal. As soon as the mandril, the form
of which is slightly conical, is introduced into the barrel it is drawn or
pushed with a force sufficient for the purpose at the same time that it is
revolved in order to describe the helicoidal trajectory of the grooves.
In making this double movement of progression and rotation, the
projections or reliefs upon the mandril in order to open out a passage
for themselves compress the fibres of the heated metal and force them
back as it were so as to mould them according to the reliefs on the
mandril.
The following is an example of the apparatus which may be used to
carry the Invention into effect. The mandril formed with projections,
the form of which is that which it is desired to impart to the rifling, is
mounted upon a shaft screwed threaded for the greater part of its length.
This screw under the action of a turning nut causes the mandril to
advance through the barrel as long as it is rotated by a toothed wheel.
The wheel or turning nut and the toothed wheel gear with two wheels
keyed upon a second shaft actuated by a pulley or directly from the
prime mover. The diameters of these wheels are calculated so as to
establish the desired relation between the movements of progression and
rotation according to the speed necessary for the grooving.
This process is applicable to all kinds of grooving. Three systems
may be mentioned as types, viz, the French, the Krupp, and the Scott.
Not only is process easy and economical, but the grooving produced
by it is very perfect compared with that by former systems.

page_text: Without going much into the details of arrangements it may becomo
preferable to employ in practice it may be well to mention that the
employment of several mandrils of graduated thickness, in order to
form the rifling by several successive passages, will be found very
advantageous as avoiding the inconveniences resulting from a too sudden
compression of the fibres.