IMPROVEMENTS IN 'DRIFTS OR TOOLS USED FOR ENLARGING HOLES, AND IN APPARATUS FOR MAKING THE SAME
Year: 1863

page_text: LETTERS PATENT to John Eglin, of Glasgow, in the County of Lanark,
North Britain, Engineer, for the Invention of "IMPROVEMENTS IN
'DRIFTS OR TOOLS USED FOR ENLARGING HOLES, AND IN APPARATUS FOR
MAKING THE SAME."
Sealed the 13th May 1864, and dated the 19th November 1863.
PROVISIONAL SPECIFICATION left by the said John Eglin at the
Office of the Commissioners of Patents, with his Petition, on the 19th
November 1863.
I, JOHN EGLIN, of Glasgow, in the County of Lanark, North Britain,
Engineer, do hereby declare the nature of the said Invention of "IMPROVE-
MENTS IN DRIFTS' OR TOOLS USED FOR ENLARGING HOLES, AND IN APPARATUS FOR
MAKING THE SAME," to be as follows, that is to say:-
This Invention relates to improved drifts of round, square, and other forms,
such as are used for enlarging holes for bolts, pins, rivets, keys, and the like
in metal plates, bars, shafts, or blocks, and also comprises improvements in
apparatus for making such drifts, the object being generally to render them
more efficient, more easily driven, and more capable of leaving the holes in a
smooth finished condition than the drifts hitherto in use.
In carrying out the Invention a steel blank is taken of a round, square, or
other required transverse section and having the usual slight taper longitudi-
nally, and a series of grooves are cut continuously upon it in equally inclined

page_text: and opposite directions, so as to form a series of diamond-shaped cutters upon
the surface. One side of the grooves forms a very obtuse angle with the sur-
face, whilst the other side forms therewith a rectangular or nearly rectangular
cutting edge, it being preferred to make this cutting edge slightly more acute
than a right angle. The inclination or pitch of the inclined grooves is made
such that the diagonal of each diamond face as measured along the drift is at
least half the other diagonal, it being preferred to make it about equal to the
other diagonal, which will cause the sides of the cutting points to form
angles of 45 degrees of the circle ou opposite sides of the longitudinal line.
The apparatus for cutting the improved drifts comprises a bracket to be fixed
on the saddle of a screw-cutting lathe and having an opening for the drift
which is held between the lathe centres. In the projecting face of the
bracket radial grooves are cut to receive movable tool holders, four such
grooves and holders being ordinarily required for drifts of ordinary sizes, which
will require four inclined grooves cut in each direction. The tool holders are
moved gradually inwards as the cuts become deeper by an external ring
formed with eccentric or inclined faces to bear on their outer ends, the ring
being turned by a toothed segment and worm. The outer ring at the parts
not acting on the tool holders is shaped conically inside to fit on a conical ring
or washer which is fixed to the bracket face and holds the outer ring in
place. A flat ring is fixed to the outer ring, and by means of eccentric or
inclined flanges acting on projections on the tool holders serves to move these
outwards when the outer ring is turned back. The arrangement described
is suitable for round drifts, but with slight modifications of its parts, and of
the lathe movements, may be made suitable for other forms.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Eglin in the Great Seal Patent Office on the 19th
May 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN EGLIN,
of Glasgow, in the County of Lanark, North Britain, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of November, in the year of our
Lord One thousand eight hundred and sixty-three, in the twenty-seventh
year of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said John Eglin, Her special licence that I, the said John
Eglin, my executors, administrators, and assigns, or such others as I,

page_text: the said John Eglin, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN 'DRIPTS' OR TOOLS FOR ENLARGING HOLES AND IN APPARATUS
FOR MAKING THE SAME," upon the condition (amongst others) that I, the said
John Eglin, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Eglin, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following state-
ment in writing; reference being had to the accompaning Drawings, and to
the letters and figures marked thereon, that is to say:--
My said Invention relates to improved drifts of round, square, and other
forms, such as are used for enlarging holes for bolts, pins, rivets, keys, and the
like in metal plates, bars, shafts, or blocks; and also comprises improvements
in apparatus for making such drifts, the object being generally to render them
more efficient, more easily driven, and more capable of leaving the holes in a
smooth finished condition than the drifts hitherto in use.
And in order that my said Invention and the manner of performing the
same may be properly understood, I have hereunto appended a Sheet of
explanatory Drawings to be herein-after referred to, and representing examples
of my improved drifts, and a modification of my improved apparatus for making
the same.
In making a drift according to my said Invention, a steel blank is taken of
a round, square, or other required transverse section, and having the usual
slight taper longitudinally, and a series of grooves are cut continuously upon
it in equally inclined and opposite directions, so as to form a series of diamond-
shaped cutters upon the surface.
Figures 1 and 2 are elevations of round drifts formed in this way; Figures
3 and 4 are a section and an elevation of a square drift; and Figures 5 and 6
are a section and an elevation of a flat drift.
A few of the diamond-shaped cutting points formed by the grooving are
marked with the reference letter a. One side of each groove forms a very

page_text: obtuse angle with the surface, whilst the other side forms therewith a
rectangular or nearly rectangular cutting edge, it being preferred to make
this cutting edge slightly more acute than a right angle. The inclination or
pitch of the inclined grooves is made such that the diagonal of each diamond
face as measured along the drift is at least half the other or transverse
diagonal, it being preferred to make it about equal to the other diagonal,
which will cause the sides of the cutting points to form angles of 45 degrees
of the circle on opposite sides of the longitudinal line.
My apparatus for cutting the improved drifts is shown in front elevation in
Figure 7, in vertical section in Figure 8, as at the centre line, and in
horizontal section in Figure 9, as at the line c, d, in Figure 7. The
apparatus comprises a bracket 1, to be fixed on the traversing saddle of a
screw-cutting lathe, and formed with a stationary chuck plate 1, in the centre
of which there is an opening 3 for the drift 4, which is round in this example,
and is held between the lathe centres, being actuated as for being formed into
a screw, but with a suitable adjustment of the speeds, as will be understood
by the practical machinist. In the front of the chuck plate 2 radial grooves 5
are formed, to receive movable tool holders, of which one, 6, is shown in
position. Four grooves, 5, are shown for four tool holders, which will be
ordinarily required for drifts of ordinary sizes, such drifts requiring four
inclined or helical grooves in each direction; it will, however, be obvious
that the chuck plate may be made to receive any convenient number of tool
holders. Each tool holder 6 is held in its groove by means of a clamp 7
screwed at the back upon a snug formed on the tool holder, and projecting
through a slot in the chuck plate. The tool holders are moved simultaneously
and gradually inwards as the cuts become deeper by an external flanged
ring 8 formed with internal eccentric grooves, which work upon a snug 9
formed on the front of each tool holder, the ring 8 being turned by a worm 10,
which gears with a toothed segment formed on it. The ring 8 is shaped
conically on the inside of its cylindrical flange 11 to fit on the edge of the
chuck plate 2, and it is held in place by a ring 12 fixed to it in two halves,
and shaped to catch the back edge of the chuck plate. The details of this
apparatus are simpler and better than those described in my Provisional
Specification relative hereto, but the mode of action is the same, and the
arrangements are mechanically equivalent. It will be understood that the
grooves running in one direction are first cut, and the grooves running in the
other direction are then cut with the traverse motion reversed. The arrange-
ment described is suitable for round drifts when used with the ordinary
motions of a screw-cutting lathe, but it may also be used for square and other

page_text: drifts if suitable movements are given to the drifts, and if the central aperture
is made large enough to admit of such movements.
Having thus particularly described my said Invention, and the manner in
which the same is or may be performed, I have to state that I do not restrict
myself to the precise details herein described or delineated, but that what I
believe to be novel and original, and claim as the Invention secured to me by
the herein-before in part recited Letters Patent, is,-
1. The making of drifts with cutting edges formed by means of continuous
grooves, shaped and disposed as herein-before described.
And, 2. The making of drifts by means of apparatus substantially such
as is herein-before described.
In witness whereof, I, the said John Eglin, have hereunto set my hand
and seal, this Seventeenth day of May, in the year of our Lord One
thousand eight hundred and sixty-four.
Witness,
EDMUND HUNT,
Patent Agent,
28, St. Enoch Square,
Glasgow.
JOHN EGLIN. (L.S.)