Improvements in Chasing Tools.
Year: 1899

page_text: I, SHIPLEY NEAVE BRAYSHAW, of Mulberry Street, Hulme, Manchester, in
the County of Lancaster, Mechanical Engineer, do hereby declare the nature of
this invention to be as follows:-
This invention relates to circular or cylindrical chasing tools for cutting single
threaded screws.
Hitherto such tools have been made by first cutting a screw on the cylindrical
end of a steel bar or tool and then grinding or cutting away a notch or gap in
the cylinder to provide a cutting face. In such a tool each thread advances in
each revolution exactly the distance of the pitch of the screw.
I have found in practice that for a tool to be employed between minimum and
maximum limits this is not the best form but that a better and more accurate
tool is produced in which a continuous thread is not formed upon the tool but
that each thread is advanced less than the pitch.
In carrying out the invention I prepare the cylindrical steel in the usual way
and first cut or grind out the gap or notch before proceeding to cut the threads.
The tool is then cut in a lathe or other machine and at each revolution of the
work the cutting tool of the lathe is advanced or moved by a cam or otherwise
a less distance than the pitch or a less distance than by a continuous thread. In
this way the thread cut upon the cylindrical chasing tool is not continuous.
This method of manufacture requires that the notch or gap must be cut before
the thread is chased thereon.
I find that by constructing cylindrical chasing tools in this manner a much
straighter thread or one at a less angle to the vertical is produced and conse-
quently there is less friction or rubbing of the thread which is being chased
against the thread of the tool and a cleaner cut is obtained.
Improvements in Chasing Tools.
I, SHIPLEY NEAVE BRAYSHAW, of Mulberry Street, Hulme, Manchester, in
the County of Lancaster, Mechanical Engineer, do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:-
This invention relates to circular or cylindrical chasing tools for cutting in-
Launol
SONOWY
threade

page_text: Hitherto such tools have been made by first cutting a screw on the cylindrical
end of a steel bar or tool and then grinding or cutting away a notch or gap in
the cylinder to provide a cutting face. In such a tool each thread advances in
each revolution exactly the distance of the pitch of the screw.
I have found in practice that for a tool to be employed between minimum and
maximum limits this is not the best form but that a better and more accurate
tool is produced in which a continuous thread is not formed upon the tool but
that each thread is advanced less than the pitch.
The invention will be fully described with reference to the accompanying
drawings.
Hitherto such tools have been made by first cutting a screw on the cylindrical
end of a steel bar or tool and then grinding or cutting away a notch or gap in
the cylinder to provide a cutting face. In such a tool each thread advances in
each revolution exactly the distance of the pitch of the screw.
I have found in practice that for a tool to be employed between minimum and
maximum limits this is not the best form but that a better and more accurate
tool is produced in which a continuous thread is not formed upon the tool but
that each thread is advanced less than the pitch.
The invention will be fully described with reference to the accompanying
drawings.
Fig. 1. Side elevation.
Fig. 2. End elevation.
Fig. 3. Sectional elevation line - Fig. 2.
Fig. 4. Sectional elevation on line y-y Fig. 5, showing a modification.
Fig.
5. Transverse section of same.
I prepare the cylindrical steel blank A in the usual way and first cut or grind
out a notch a before beginning to cut the threads B. This is necessary as the
thread not being continuous it would be impossible to cut it were the notch a
not first cut out
The tool is cut in a lathe or other machine and at cach revolution of the
work the cutting tool of the lathe is advanced or moved by a cam or otherwise
a less distance than the pitch or a less distance than by a continuous thread. In
this way the thread cut upon the cylindrical chasing tool is not continuous.
The chaser shown in the drawings has 5 threads per inch-and-the-advance-of
the thread per revolution is 12 inch.
In Figs. 4 & 5 a modification of the tool is shown in which the cutting or
chasing part is made separate from the shank and is attached thereto by a screw
thread or otherwise. The construction of the threads of the chaser are the same
as that previously described.
.
I find that by constructing cylindrical chasing tools in this manner a much
straighter thread or one at a less angle to the vertical is produced and conse-
quently there is less friction or rubbing of the thread which is being chased
against the thread of the tool and a cleaner cut is obtained.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed I declare that what I
claim is:
1. A cylindrical chasing tool constructed with a thread which is not con-
tinuous but is advanced in one revolution less than the pitch substantially as
described.
2. A chasing tool constructed substantially as described and shown.
lay of November 1899.
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.