IMPROVEMENTS IN SCREW CUTTING STOCKS OR TOOLS
Year: 1878

page_text: LETTERS PATENT to Auguste Pierre Bara, of 40, Rue du Bac, Paris, France,
Engineer, for the Invention of "IMPROVEMENTS IN SCREW CUTTING STOCKS
OR TOOLS."
Sealed the 13th June 1879, and dated the 18th December 1878.
PROVISIONAL SPECIFICATION left by the said Auguste Pierre Bara at the
Office of the Commissioners of Patents on the 18th December 1878.
AUGUSTE PIERRE BARA, of 40, Rue du Bac, Paris, France, Engineer. " IMPROVE-
MENTS IN SCREW CUTTING STOCKS OR TOOLS."
The object of my Invention is to produce in screw cutting machines, worked
either by machinery or by hand, a considerable economy of material, as well as a
great saving of labour and time.
This by a system of rectilinear guides and rational cutters. The present Specifi-
cation refers particularly to the application of my contrivance to screw cutting
stocks, and is fully shown in the accompanying Drawing.
Figure 1 is an elevation of the entire tool; Figure 2, a plan; and Figures 3 and 4,
an elevation and side view of guides and cutters.
Figure 1 shows the elevation provided with its two rectilinear guides a, b, and
cutters c; these guides and cutter are seen separately at Figures 3 and 4.
The two guides are grooved lengthwise after the form and pitch of the screw to
be made. The stocks consist of a frame A, with a square opening to receive, and in
which move the aforesaid guides a, b, Figures 1 and 2. Another cavity or bed
receives the screw cutting tool itself c, as shown in the same Figures. This tool is
grooved longitudinally, as are the guides, at the required pitch, but guides of
certain sizes suffice to make the several pitches which are its divisors. The screw
cutting tool is set firm in its bed by the key d passing through the frame A,
Figures 1 and 2, and its nut 6.

page_text: The length of the cutting tool and its particular form, which is similar to that of
a common lathe screw cutting tool, enables it to be ground nearly as far as the top,
and is constantly kept to its cutting position by fastening the nut e of the key d.
The guides, which are of two pieces a, b, Figures 1, 2, 3, 4, are held together by
two plates i, j, and screws i, j, shown by Figures 1, 2.
The manipulation of the system is very simple, and similar to that of the common
stocks at present in use. The screw handle f, Figures 1, 2, brings the guides a, b,
from or to the cutting tool and upon the piece to be screw cut. The disposition of
the guides and cutting system enables it to take any odd diameter, and be centered
upon it without removing any piece whatever.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Auguste Pierre Bara in the Great Seal Patent Office on the 16th
June 1879.
AUGUSTE PIERRE BARA, of 40, Rue du Bac, Paris, France, Engineer.
MENTS IN SCREW-CUTTING STOCKS OR TOOLS."
"IMPROVE
The principle of this new system of male and female screw cutting apparatus is
based upon the generation of any helicoidal curve by means of right lines suitably
inclined and tangent to the cylinders.
The object of the present Specification is the application of this principle to
straight cutting tools, with or without rectilinear generating guides, according to
whether the screw cutting tools, combined in number, mutually guide each other,
or whether, combined with guides, their course during the operation is regulated by
the latter.
The principle and the first application of this system to hand screw stocks is
shown in Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 of Sheet I. of the accompanying two
Sheets of Drawings.
Figure 11 shows the principle applied to three screw cutting tools c, which mutually
guide each other.
Figures 4 and 5 show the screw cutting tool c combined with two guides a, b.
Figures 1, 2, 3, show a face view, a side elevation, and a plan of a hand screw
stock based upon the principle of the cutting tool and rectilinear generating
guides.
Figure 1 shows a face view of the screw stock provided with one single cutting
tool c, combined with two rectilinear guides a, b; one of the guides a and a cutting
tool c are represented detached in Figures 6, 7, 8, 9, 10.
These two guides, as well as the cutting tool, are grooved correspondingly to
the section of the thread which it is desired to cut, triangular, square, round, &c.
The screw stock consists of the part g, Figures 1, 2, 3, with a hole in the centre
to receive the guides a, b, and another cavity in which the screw cutting tool c is
adapted and moved.
This latter is firmly held in place by means of a key d tightened by the nut e.
The screw cutting tool c can be ground or sharpened as it wears off, and is con-
stantly brought back to the proper position by the key d.
The guides a, b, are held in place by two plates o, o, applied on both faces of the
screw stock.
The operation of this screw stock is exactly similar to that of all other screw
stocks.
The screw handle f serves to move the generating guides towards the cutting tool
or away from it, according to the diameters.
Whatever the diameters may be the guides will always be tangent, and the screw
cutting tool well centered, which permits to cut threads of the same pitch on bars
of any desired diameter without changing anything on the screw stock.
absolutely necessary that the guides and the cutting tool be grooved in the direction
opposite to that of the thread which it is desired to obtain."
It is
APPLICATION OF THE SYSTEM TO SCREW-CUTTING AND TAPPING MACHINES,
TO LATHE-CHUCKS, &C.
Figures 12 and 13 of Sheet II. represent the application of the system to screw
cutting and tapping machines, lathe chucks, &c.
g is a plate having on its outer face a dove-tailed groove, in which are adapted
and move two slides h, i, the first of which, h, carries the two rectilinear generating
guides a, b, whilst the other, i, forms the actual tool carrier, having a lateral groove

page_text: to receive the cutting tool c. This cutting tool is rigidly held by means of a set
screw d.
The under part has two cam-grooves e, e, open towards the slide.
Two studs q, fixed on the guide and tool-carriers, are engaged in the cam-grooves,
and in this manner produce the movement of the guides and the cutter toward or
away from each other, according to whether the head fis turned in one direction
or the other; this head f is engaged in a helicoidal groovej cut on the shaft or
sleeve of the head g.
Figures 14, 15, 16, show an application of the system with three screw cutting
tools, which mutually guide each other, applicable to screw cutting and tapping
machines, lathe-chucks, &c.
This mechanism is constructed in the following manner :-A head g, Figures 14,
15, 16, has in its outer face three cavities, in which are adapted and move the three
cutter carriers i, i, i, provided with their screw cutting tools c, which are inserted in
cavities formed for the purpose in the cutter carriers. On the sleeve of the head g
is loosely mounted a conical collar k, to which are loosely connected the upper ends
of the three cutter carriers i, i, i, by means of three screws m sliding in three small
slides formed in the cone of the collar k. The cutter carriers are held in their
respective places by means of washers n, Figures 14, 15, 16. The screw cutting
tools are held and locked by means of the screws p.
It will be seen that by turning to the right or left the lever 1, Figures 15 and 14,
the tool carriers are pressed in or out according to the cone of the collar, and in this
manner the position of the tools is regulated according to the diameter desired.
I claim as my Invention,---
Cutting and tapping of all kinds of threads without exception by means of a
mechanism, the construction of which is based upon the application of the above
mentioned principle, namely, the generation of any helicoidal curves by straight
tangent lines, or straight cutting tools, with or without rectilinear generating
guides.
In witness whereof, I, the said Auguste Pierre Bara, have hereunto set my
hand and seal, this Thirteenth day of June, in the year of our Lord One
thousand eight hundred and seventy nine.
CHARLES AUTIER,
40, Rue du Bac,
Paris.
Witness.
AUGUSTE PIERRE BARA. (L.S.)