AN IMPROVED APPARATUS FOR CUTTING TENONS
Year: 1865

page_text: LETTERS PATENT to William Tighe Hamilton, of Upper Rathmines,
Dublin, for the Invention of "AN IMPROVED APPARATUS FOR CUTTING
TENONS."
Sealed the 27th April 1866, and dated the 13th November 1865.
PROVISIONAL SPECIFICATION left by the said William Tighe Hamilton
at the Office of the Commissioners of Patents, with his Petition, on
the 18th November 1865.
I, WILLIAM TIGHE HAMILTON, of Upper Rathmines, Dublin, do hereby
5 declare the nature of the said Invention for "AN IMPROVED APPARATUS FOR
CUTTING TENONS," to be as follows:-
Two circular saws are mounted upon the same axle upon the principle
commonly known as that of the "drunken saw," their distance apart and
angle of inclination being such that the interval between their respective
0 ranges is equal to the thickness of the tenon. The wood is advanced endways
upon these with such peculiar motion that while each saw cuts away one side
of the tenon the shoulders are left square. This motion is effected by a frame
Its action
which continually presents the shoulder as a tangent to the saw.

page_text: is due to the principle of two unequal radii, whose centres are in the same
line as that of the saw; these are united by a pivot at the circumference
of the saw; the centre of the shorter is fixed, that of the longer is
capable of alternate motion by a sliding or radial arrangement. At first
the wood is below the saws; then the elevation of the frame by a lever or a
rack and pinion draws forward the moveable centre, and as the wood passes
the saws the operation is completed. The exact lengths of the radii and the
distance of their centres from that of the saw depend upon its size, and must
be ascertained by calculation or experiment. It will, however, be found that
the shorter is equal to about one and the longer to two diameters of the
saw; and that the centre of the former is distant about one and a half and
of the latter about two and a half of such diameters from the centre of the
The operation may also be above the line of centres.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Tighe Hamilton in the Great Seal Patent Office on
the 12th May 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
TIGHE HAMILTON, of Upper Rathmines, Dublin, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of November, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of Her reign,
did for Herself, Her heirs and successors, give and grant unto me, the said
William Tighe Hamilton, Her special licence that I, the said William Tigbe
Hamilton, my executors, administrators, and assigns, or such others as I, the said
William Tighe Hamilton, 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 "AN IMPROVED APPARATUS
FOR CUTTING TENоNя," upon the condition (amongst others) that I, the said
William Tighe Hamilton, my executors or adininistrators, 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Tighe Hamilton, do hereby declare

page_text: the nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
Two or more circular saws are mounted on the same spindles in the manner
commonly called that of the drunken saw, their distance apart and inclina-
tion are such as to correspond with the desired thickness of the tenon. The
wood is advanced endways upon these with such peculiar motion that while
the saws cut away the sides of the tenon its shoulders are squared. This is
effected by means of a frame which continually presents the shoulder as a
tangent to the saw. The frame is composed of two unequal radii, whose
centres are in the same line as that of the spindle, one centre being at a
distance of about twice and the other at that of once the diameter of the
saw from its circumference. At a distance of one inch from the circumference
these radii are pivoted together. The centre of the shorter radius is fixed,
that of the longer is moveable horizontally. The wood being placed in the
frame a rack and pinion movement causes it to pass up in front of the saws,
the moveable centre of the longest radius being drawn forward, so that the
point of contact with the saw continually describes a right line. The relative
lengths of the radii may be varied. Their exact proportions are best obtained
by experiment. Eccentric saws may be used for bevilled and elliptic saws
for carved work.
In witness whereof, I, the said William Tighe Hamilton, have hereunto
set my hand and seal, this Tenth day of May, in the year of our Lord
One thousand eight hundred and sixty-six.
WILLIAM TIGHE HAMILTON. (L.s.)