An Improved Adjustable Attachment to Brace Bits for use in Boring and Countersinking Holes for the Reception of Screws.
Year: 1891

page_text: * Date of Application, 14th Nov., 1891-Accepted, 24th Dec., 1891
COMPLETE SPECIFICATION.
An Improved Adjustable Attachment to Brace Bits for use in
Boring and Countersinking Holes for the Reception of Screws.
I, THEOPHILUS OSBORN SMITH, of Medley on Thames Oxford Yacht & Boat
Builder do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
This invention relates to an improved attachment to bits for use in boring and
countersinking holes for the reception of screws, in hard wood and other substances,
and consists of a cylindrical stop or gauge composed of steel or other suitable
metal having a hole drilled through the same longitudinally.
Through the said hole is passed the cutting point of the bit, and means are
provided as hereinafter described for rigidly fixing the gauge at any desired point
on the length of the bit, and by which the precise depth of the hole to be bored
can be pre-determined.
The countersinking of the hole is effected by the employment of a blade situate
at the end of the gauge and presenting an inclined cutting edge towards the
bit point. This countersinking blade is formed in one piece with a shaft or
spindle which is passed through the longitudinal hole in the gauge and bearing
against the concave surface of the bit, and in order that the said blade may be
moved up or down according to the depth of the countersinking required a short
slot is formed in the gauge from its lower surface upwards corresponding in length
and width to that of the countersinking blade. As mentioned above the counter-
sinking blade and its spindle is arranged to lie against the concave or hollow surface
of the bit, so that the countersinking or inclined edge of the blade extends to a
point within the circumference of the hole bored, and by this means the counter-
sunk hole is cleanly cut leaving no ragged or torn edge.
For the purpose of securing the gauge and countersinking device at any required
point on the bit, a screw threaded hole is formed through the gauge near to its
upper end in which is inserted a short screw pin furnished with a butterfly head
the other end of the pin being arranged to bear against the spindle of the
countersinking blade, pressing it tightly against the bit and so firmly securing the
whole device.
For the better explanation of my said invention I append the accompanying
sheet of drawings in which
Figure shews my improved apparatus adjusted for the formation of a large
screw hole and Fig. 2 for the boring of a small screw hole.
In both figures a represents the gange through which are inserted the bit d and
the spindle of the countersinking blade b, is indicated by dotted lines.
The butterfly-headed screw pin for securing the whole in any required position
is marked e, and in order that the countersinking device may not accidentally
drop out on the screw pin being loosened, the end of the spindle is enlarged or
turned over as at c, so that the countersinking device cannot be entirely removed
unless the bit is first drawn out.
The extent of the slot in the lower part of the gauge a, to admit of the blade b,
being moved up or down as required is shewn by a transverse dotted line at f, and
in some cases I may enlarge a portion of the slot to serve as a clearance aperture
for wood cuttings or shavings. I may make the blade 6 straight in vertical section,
or I may form it with a slight curve so as to present the cutting edge more directly
in opposition to the material to be cut as the bit revolves.
My said invention is capable of various unimportant modifications without
departing from the general principle thereof. For instance I may permanently fix

page_text: the inclined countersinking blade at the bottom surface of the gauge, and regulate
the depth to which it cuts into the wood by means of a check stud carried on a
spindle similar in other respects to that above mentioned, or such spindle may
travel by means of a horizontal screw movement actuated by a separate screw pin
to that which bears on the bit, so that the said check stud can be moved up or
down and so regulate the extent of the countersinking.
Although the above described device can be readily applied to any ordinary bit,
it can be most advantageously and conveniently used in combination with a special
made bit having a scale of inches and fractions of an inch marked thereon, so that
the gauge can be adjusted for any predetermined length screw hole without the
necessity of measuring the distance from the bit-point to the gauge with a rule, in
which there is a liability of inaccuracy.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
(1) The improved adjustable attachment to brace bits provided with an adjustable
countersinking blade the whole device being fixed to the bit by means of a screw
pin or pins, all substantially as herein before described in this Specification and
illustrated by the accompanying drawings.
(2) A hole-boring and countersinking device for attachment to brace bits con-
sisting of an adjustable block provided with a mutilated conically shaped cutting
head for countersinking, this block being provided with a screw adjustable stop to
regulate the depth of countersinking required.
Dated this 14th day of November 1891.
GEO. H. RAYNER,
37, Chancery Lane, W.C., Agent for the Applicant.