MACHINE FOR CUTTING SCREW THREADS ON AUGERS, AND FOR TURNING AND PREPARING THE POINTS OF AUGERS PREPARATORY TO CUTTING THE SCREW THREADS THEREON."
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Peter Mackay at the Office of the
Commissioners of Patents on the 26th January 1878.
"
A
PETER MACKAY, of Glasgow, in the County of Lanark, North Britain.
MACHINE FOR CUTTING SCREW THREADS ON AUGERS, AND FOR TURNING AND
PREPARING THE POINTS OF AUGERS PREPARATORY TO CUTTING THE SCREW THREADS
THEREON."
This Invention, which relates principally to a machine for cutting the screw
threads on the points of augers, viz., those screw threads by means of which the
entrance of the auger into the wood wherein a hole is to be bored by the auger is
effected, has for its object to dispense with the manual operation of cutting the 'said
screw threads up to the present time employed.
The machine constituting the present Invention consists of a headstock fitted
with a hollow mandrill carrying a driving pulley, and provided with spur wheels
and pinions after the manner of a back-geared lathe for the purpose of changing the
speed from fast to slow as required. This mandrill is made hollow for the purpose
of allowing an auger on the point of which the entering threads have to be cut to be
passed through, the mandril being provided at one end with gripping jaws for the
purpose of holding the auger concentrically with its own axis.
On the bed of the machine on which the aforesaid headstock, mandrill, and
gearing are carried, there is also fitted the apparatus by which the entering screw
threads of the auger are cut.
This apparatus is capable of being moved backwards and forwards on the bed,
and being fixed thereon in any required position.
This apparatus is fitted with a pair of levers or arms which are capable of being
moved on their axis, so that their upper extremities may be varied to any required
distance apart. The upper extremity of each of these levers carries a small driving
pulley, to the axis of each of which is fitted a hardened and tempered steel disc, the
edges of which discs are of the form corresponding to the shape of screw thread
required to be cut on the edge of the point of the auger.
The edges of the discs are also formed with cutting teeth after the manner of the
teeth of a file, so that as they revolve quickly on opposite sides of the slowly
revolving auger point, the two threads required to be formed on the same point are

page_text: thereby cut, each disc being placed at the angle corresponding to the inclination of
the screw threads, and the two discs being at opposite sides of the auger being cut
at angles equally but oppositely inclined.
The hollow mandrill herein-before referred to is provided with changeable screw
matrices, the screw threads on which correspond with the different pitches of screws
required for the different sizes of anger points.
The portions of screw nuts attached to levers which can be pressed on to or
withdrawn from the screw matrices, are also provided so that when pressed on the
screw matrices attached to the hollow mandrill they cause the screw matrix in
revolving, and therefore the mandrill together with the anger carried therein, to be.
advanced forward at the rate corresponding to the pitch of the screw thread on the
matrix.
The front part of the hollow mandrill is fitted with a collar within which it
revolves, this collar carrying a shaper corresponding to the form of the auger point,
and as the mandrill is advanced in the manner herein-before described, this shaper
acting upon the levers or arms which carry the revolving cutters, causes then to be
closed as the cutting proceeds from the larger to the smaller end of the auger point,
thus insuring a uniform depth of screw threads, and any desired shape of screwed
point over the entire surface of the point.
The pressure for forcing the cutting discs against the point on which they have
to operate is effected either by a hand lever, or by a spring or weights.
Attached to the headstock is an apparatus for squaring, turning, and otherwise
preparing the point of the auger preparatory to cutting the screw thereon, which
apparatus is arranged so as to be readily moved out of the way after it has done its
work, so as not to interfere with the working of the screw cutting apparatus.
The said apparatus consists of a sole plate, on which slides a holder carrying the
tool for preparing the point of the auger.
The sole plate has in it undercut guide grooves in which corresponding pro-
jections on the tool holder take.
When this apparatus is in operation the tool is brought up to the revolving
auger in the direction to form the shoulder for the auger at the root of the screw
by the tool holder being guided in a groove in the sole plate, the said groove
running in a direction at right angles to the axis of the auger being operated
upon.
When the shoulder has been cut to the proper depth, the projections on the tool
holder come opposite side grooves in the sole plate, the said grooves running out of
the before-mentioned groove, and taking any desired curved or other course by
which the tool, when the tool holder is guided along these grooves, will have the
requisite change of motion imparted to it for cutting the point of the auger of the
required form.
The movement of the tool holder along the grooves in the sole plate may be
effected by hand levers, screws, or by any other suitable means.