IMPROVEMENTS IN EXPANSIVE BITS
Year: 1858

page_text: LETTERS PATENT to William Alanson Clark, of Bethany, in the County
of New Haven, and State of Connecticut, United States of America, for
the Invention of "IMPROVEMENTS IN EXPANSIVE BITS."
Sealed the 30th September 1858, and dated the 24th April 1858.
PROVISIONAL SPECIFICATION left by the said William Alanson Clark
at the Office of the Commissioners of Patents, with his Petition, on the
24th April 1858.
I, WILLIAM ALANSON CLARK, of Bethany, in the County of New Haven,
and State of Connecticut, United States of America, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN EXPANSIVE BITS," to be
as follows:-
:
In the construction of a movable cutter and the recess in which it is
secured, by which the edge of the cutter is relieved from pressure and
effectually secured from vibration in the stock while operating. A groove is
formed in the movable cutter back of its cutting edge; this groove is
supported upon a V-shaped ledge in the stock, while at the same time it is so
keyed at the top as to effectually keep the cutter from vibrating in the stock.:
In the combination of a movable cutter, having a bevel with a bevelled
plate or follower for securing it in place, said plate being drawn up by a screw
or otherwise, as may be convenient or desirable.

page_text: And in arranging the movable and stationary cutters in relation to each
other, so that the stationary cutter shall deliver its chips in front of the
movable cutter. The construction of the shank and of the cutting lip
permanently attached to it are very much the same as those of other expansive
bits, but the mode of securing the movable cutter in its place is different.
In my bit a V-shaped ledge rises from the bottom of the recess in which the
cutter is secured to receive the V-shaped groove in the movable cutter. The
form of this groove and of the ledge upon which it rests is such as to give a
firm bearing to. the cutter and draw it singly against the back of the recess
when the pressure is applied, which secures said cutter in place. The mode
of securing the cutter is by means of the bevelled plate or follower, driven
home by a screw in such a manner as to press the cutter against the back
side and bottom of the recess in which it is secured. The relative positions
of the cutters are such as to deliver the chips from the stationary cutter upon
the back side of that part of the stock which supports the movable cutter,
and this involves the necessity of cutting away the stock to allow the chips
to pass. This, of course, weakens that part of the stock and makes it
necessary to secure sufficient strength by retaining more metal on the side
upon which the cutter is attached, and as a consequence the edge of this
cutter is thrown out too far from the centre of the stock, and its efficiency of
operation in different positions is thereby reduced. To obviate this difficulty
I have conceived the plan of forming the lip upon the stock in that position,
by which the chips from it are delivered upon that side of the stock which is
cut away to receive the cutter; this allows the opposite side to be left
entire, and also so balances the operating parts as to relieve the screw from a
portion of the pressure which would otherwise be thrown upon it when in
operation.
It may be considered desirable in the construction of very large bits to
leave a portion of metal in front of the movable cutter for the more effectual
support of that side of the bit. The seat upon which the movable cutter
rests at the bottom, has, as in most expansive bits, an inclination corresponding
with that of the edge of the cutter. To make the depth cut as nearly equal
as possible, I make the edge of the longer cutters so that it shall stand a
little higher in the stock than the edges of those which are intended to cut a
smaller hole. There are other modifications and arrangements of the Invention
that will be more particularly described in the Final Specification.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Alanson Clark in the Great Seal Patent Office
on the 23rd October 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, J, WILLIAM
ALANSON CLARK, of Bethany, in the County of New Haven, and State of
Connecticut, United States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of April, A.D. One thousand
eight hundred and fifty-eight, in the twenty-first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto me, the said William
Alanson Clark, my executors, administrators, and assigns, Her special license
that I, the said William Alanson Clark, my executors, administrators, and
assigns, or such others as I, the said William Alanson Clark, 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 EXPANSIVE BITS," upon the
condition, amongst others, that I, the said William Alanson Clark, or my
executors, administrators, and assigns, 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 William Alanson Clark, 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 statement, that is to say:-
My said Invention consists, in,-
First, the mode herein-after described of constructing the movable cutter,
and the recess in which it is secured, by which the edge of this cutter is
relieved from pressure, and effectually secured from vibration in the stock
while operating, as herein-after more fully set forth.
:
Second, in the combination of a movable cutter, bevelled as described, with
a bevelled plate or follower for securing it in place, as described, said plate
being drawn up by a screw, or otherwise, as may be convenient or desirable.
Third, so arranging the movable and stationary cutters in relation to each

page_text: other, that the stationary cutter shall deliver its chips in front of the movable
cutter, as described; the parts being so arranged that all the chips made by
the instrument shall be delivered upon one and the same side of the shank
of the bit, thereby allowing the other side of said shank to be left entire to
support the working parts, any recess on the back side of the shank to allow
the chips to pass being by this device rendered unnecessary.
In the accompanying Drawings, Figure 1 is a side elevation of my improved
bit; Figure 2 is also an elevation, showing the side opposite to that shown in
Figure 1; Figure 3 is an elevation, its plane of projection being transverse
to Figures 1 and 2; Figure 4 is a sectional elevation, its plane of projection
being parallel to that in Figure 3, but transverse to that of Figures 1 and 2 ;
Figure 5 is a side elevation of the movable cutter; Figure 6 is a reverse
view of it; Figure 7 is an end elevation; Figure 8 is an inverted plan, or, in
other words, an under side view; Figure 9 is a back side elevation of a cutter
so made as to always keep the movable cutter at just the same distance behind
the point of the bit, while, at the same time, the depth of wood left to support
the central portion of the bit is varied by the adjustment of said cutter.
Figure 10 is a side elevation of a bit, embodying the same novel features
as represented in the previous Figures; but the stationary cutting lip is
formed in such a position upon the bit as to throw its chips in front of the
movable cutter, which arrangement avoids the necessity of filing away the
back side of the bit to allow the chips to pass; Figure 11 is an elevation, trans-
verse to Figure 10; Figure 12 is a back side elevation of the same bit;
Figure 13 is a vertical section showing the same movable cutter secured in the
'same way in a mortice instead of in a recess in the body of the bit.
Bits with movable cutters secured in a mortice in the shank or stock have
been long known; but the modes which have been adopted for securing these
cutters have been more or less objectionable, so much so as to interfere with
their general use; one objection is that the bit, or more properly, the movable
cutter, being secured by being keyed down upon the bottom of the mortise,
the cutting edge of this movable cutter rests upon the middle of the stock,
which not only destroys the cutting edge of wood boring tools, but also pre-
'cludes such an arrangement as would allow a greater depth of wood to be left
contiguous to the central cutter or stock to support it when a larger cutter
is put in, or a larger hole bored which requires such support for the stock.
My first improvement forms a groove in a movable cutter back of its cutting
edge and supports this groove upon a V-shaped ledge in the stock, while at the
same time it is so keyed at the top as to effectually keep the cutter from
vibrating in the stock...

page_text: The combination of parts embodied in my second improvement also conduces
to the prevention of vibration by its peculiar mode of securing the bit.
In the Drawings, A is the shank of the bit, upon which the inner or station-
ary cutter is formed, and in which the recess or mortise is made which receives
the movable cutter B. The construction of the shank and of the cutting lip
permanently attached to it have very much the same as those of other expansive
bits; but the mode of securing the movable cutter B in its place is different.
In my bit a V-shaped ledge a rises from the bottom of the recess in which the
cutter B is secured, to receive the V-shaped groove 6 in said movable cutter;
the form of the ledge a, and that of the groove b, are shown in Figures 3, 4,
11, and 13; the form of the groove is also shown in Figure 7; the form of
this groove b, and of the ledge upon which it rests, are such as to give a firm
bearing to the cutter B, and to draw it snugly against the back of the recess
when the pressure is applied, which secures said cutter in place. The mode
of securing this cutter is by means of the bevelled plate or follower D, driven
home by a screw E in such a manner as to press the cutter B against the
back side and bottom of the recess in which it is secured, said cutter being
also bevelled, as shewn, to facilitate the accomplishment of this purpose; the
bevel of the upper edge of the plate D being an under cut bevel so as to allow
the back side of said upper edge to always come home against the flat seat
behind it upon the stock, and also serving the further purpose of keeping said
follower in place, when the screw E is loosened for the adjustment or removal
of the movable cutter. The form and arrangement of these parts are shown
in Figures 1, 3, 4, 10, 11, and 13.
In the first four Figures the relative positions of the cutters are such as to
deliver the chips from the stationary cutter C upon the back side of that part
of the stock which supports the movable cutter, and this involves the necessity
of cutting away the stock, as shown at e in Figures 2 and 3, to allow the chips
to pass; this of course weakens that part of the stock, and makes it necessary
to secure sufficient strength by retaining more metal on the side upon which
the cutter B is attached; and as a consequence, the edge of this cutter is thrown
out too far from the centre of the stock, and its efficiency of operation in
different positions is thereby reduced. To obviate this difficulty I have con-
ceived the plan of forming the lip C in that position upon the stock in which
it is represented in Figures 10, 11, 12, and 13; by which arrangement the
chips are delivered upon that side of the stock which is cut away to
receive the cutter B, and upon which the cutter B delivers its chips, thus
delivering all the chips upon one side and allowing the other side to be left
entire, to give the necessary strength; and also so balancing the operating

page_text: parts as to relieve the screw J from a portion of the pressure which would
otherwise be thrown upon it when in operation. This arrangement enables
me to bring the edge of the cutter B nearly back to the centre of the stock,
as shown in Figure 11, and in large bits it may be brought further back than
is there represented as being placed.
It may
in some cases be considered desirable, in the construction of very
large bits, to leave a portion of metal in front of the cutter B, as shown in
Figure 13, for the more effectual support of that side of the bit. In this case
the screw E should extend through this part, as, shown.
The mode which I have above described of supporting and securing the
cutter B, supports it without its resting on the cutting edge; and in my con-
struction, space is left under the cutting edge, as shown, and by thus supporting
it, the edge of a large cutter may be set higher in the stock than it is necessary
or best to set the edge of a small one, which allows more wood to be left near
the stock to support it, when a large cutter is used. The cutting edge of the
cutter B is inclined so as to bring its working end lower than the other, for
the twofold purpose of causing the unemployed end to clear the wood, and of
leaving a portion of the wood around the central portion of the bit to support
it, while, at the same time, the outer end of the cutter B shall cut nearly or
quite as far in advance as the inner cutter. The seat upon which the movable
cutter rests at the bottom has, in most expansive bits, an inclination cor-
responding with that of the edge of said cutter, and this feature is retained in
When so con-
my bit as represented in all the Drawings except Figure 9.
structed, the sliding of the movable cutter outward also carries its working end
downward, so that when placed in its extreme outward position it will cut
considerably deeper than when withdrawn so as to cut its minimum hole. It
is desirable, however, that the depth it will cut shall be as nearly equal as
possible; and, further, it becomes necessary when the movable cutter is
required to cut away a very large amount of wood, to preserve a considerable
shoulder of the wood adjacent to the stock, for its support against the strain
imposed upon it by the resistance against the removable cutter. For this purpose
I make my longer cutters so that the edge shall stand a little higher in the
stock than the edges of those which are intended to cut a smaller hole, which
my mode of supporting the cutters upon a ledge or shoulder placed above the
edge enables me to do; and this provision for giving the proper shoulder and
depth of cut answers very satisfactorily for most purposes.
Should greater
nicety in these respects be desirable, it may be attained by the adoption of the
cutter shown in Figure 9, and the use of a horizontal V in the stock, as in
this case the edge of the cutter is inclined with reference to the groove b,

page_text: while in the cutter shown in the previous Figures it is parallel to it. This
arrangement causes the point of the movable cutter to always work at the
same depth, and makes the depth of the shoulder in exact proportion to the
distance at which the point of the cutter is set from the centre.
The particular improvements which constitute my said Invention, and which
I claim as having been originally and first invented by me, are,-
First, the combination of the V-shaped projection or seat a, or its equivalent
with the corresponding groove in the movable cutter above the cutting edge,
by which I am enabled to vary the distance of the edge of the cutter B,
near the stock above that of the central cutter to any desirable extent,
substantially as and for the purposes set forth.
Second, the combination of the movable cutter B, bevelled as described, with
the bevelled plate or follower D and screw E, for securing the cutter B to the
body of the bit substantially as set forth.
Third, the construction of the parts and arrangement of parts in relation
to each other, herein described, by which all the chips made by the instrument
are delivered upon one and the same side of the shank of the bit, thereby
allowing the back side of said shank to be left entire, as set forth.
In witness whereof, I, the said William Alanson Clark, have hereunto
set my hand and seal, this Fifth day of October, in the year of our
Lord One thousand eight hundred and fifty-eight.
WILLIAM ALANSON CLARK. (L.S.)