Improved Mortising Chisel..
Year: 1889

page_text: Date of Application, 2nd Dec., 1889
Complete Specification Left, 26th Aug., 1890-Accepted, 27th Sept., 1890
PROVISIONAL SPECIFICATION.
Improved Mortising Chisel..
I, RALPH WALDO LITTLE, Carpenter, a subject of the Queen of Great Britain and
Ireland, now residing at 408 East 114th Street in the City of New York, County and
State of New York, one of the United States of America, do hereby declare the
nature of this invention to be as follows:-
The purpose of my chisel is to cut the wood and at the same time take it out of
the mortise, and it is accomplished by constructing a chisel with three sides, together
forming in cross section, three sides of a rectangular trough, open at one side, having
very thin walls, the outer and inner surfaces of each wall or side lying in planes
respectively parallel to each other and the middle or cross wall or side being at right
angles to the other two sides or walls which are joined to or rather formed on its side
edges, thus strengthening and supporting it and permitting the use of walls so thin
that, alone, any one would be too weak for use.
The extremities of all three walls of the chisel extend so as to lie in the same
horizontal plane, assuming the chisel to be vertically placed, but only the middle side
or blade is brought to a cutting edge, the others though very thin being ground off
substantially flat.
At some distance from the cutting edge of the middle blade (where the part to be
used for cutting, by successive grindings is intended to end, or a little above) the
trough formed by the three sides is run out, preferably in a gentle curve or slant
extending from the inner surface of the cutting blade to a line drawn from the side
extremity of one of the side blades to that of the other, and the tool, above this turn
out, solid usually for a considerable distance and provided with a tang or other
device for connection with a handle, or the bar of a machine.
The cutting blade may be sharpened either from the inner or outer surface.
The advantages over earlier forms of mortising chisels are these ;
First. Leaving the side edges unsharpened, causes their action to be that of a cut
nail (crushing the wood) as distinguished from that of a sharpened wire nail, (wedging
it apart and thereby tending to split it) and as the tool is always intended to be used
with said edges parallel with the grain of the wood they do not need to be sharpened;
Second. Constructing the blades to all extend to the same plane, ensures the wood
will be separated from the wall of the mortise on three sides;
Third. Providing the three sides, permits the use of so thin blades that the wedge
like action of cutting blades is reduced to a minimum and the tool is easier driven;
Fourth. Having only three sides the interior channel is not likely to clog, were it four
sided and sharpened from within, it would scribe out a larger chip than the hollow
could release without force, requiring more power, and if from without would be more
like a wedge when inserted in the wood and the pressure of the latter would tend to
crush in its walls;
Fifth. Having a considerable solid part above the point where the blades spring,
permits the force of the blow to be disseminated through a considerable mass and the
resulting vibrations of the atoms of the blade are less, rendering them less liable to
fracture.
Dated this 16th day of November 1889.

page_text: COMPLETE SPECIFICATION.
Improved Mortising Chisel.
I RALPH WALDO LITTLE of Number 18 Sydney Place, Oxford Street, Liverpool in
the County of Lancaster, do hereby declare the nature of my invention for an
"IMPROVED MORTISING CHISEL" and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement and
accompanying drawings
My said invention relates to an improved construction of chisel for mortising wood
so arranged as to cut the wood and take it out of the mortise. This I accomplish by
forming part of the chisel with three sides together forming a trough as shown
in Fig. 3 of the accompanying drawings which is a cross section through A B of Fig. 1.
The outer and inner surfaces of the trough are parallel to each other for the greater
part of their length and the bottom of the trough is at right angles to the sides.
The sides and bottom of the trough terminate at the cutting end in a plane nearly
at right angles to the line of action of the chisel.
At some distance from the cutting edge the parallel part of the trough ceases and
runs out either by a gentle curve or an incline as shown at C C in Figures 1 and 4
which represent longitudinal sections of mortising chisels made in accordance with my
said invention. The part of the chisel beyond the part C C¹ is solid and is formed
with a tang or other device for attachment to a handle if the chisel is to be used by
hand or with the usual means for attachment to a tool holder in case the chisel is to be
used in a mortising machine as is well understood.
Figures 2 and 5 show the chisels in plan and require no further description.
The sides of the trough shaped part of the chisel are made as thin as is compatible
with the rigidity necessary to resist the compressive stress to which the chisel is
exposed when at work. The proportions shown in the drawing are those which I have
found suitable for average work.
In my Provisional Specification I referred to certain advantages obtainable by
leaving the sides of the trough without the usual bevel at the cutting end of the chisel
but further experience has led me to modify my views and I find that in most cases it
is advisable to bevel the cutting extremities of all three sides of the trough shaped
part of the chisel in the manner shown in Figures 4 and 5.
Figures 1 and 2 show a chisel in which only the bottom of the trough shaped part
of the chisel is bevelled at the cutting end while the sides are left flat.
The cutting edges may have their bevels so arranged as to be sharpened either from
the inside or the outside.
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―
A mortising chisel formed with a trough shaped working part in which the sides of
the trough are at right angles to each other and terminate in a plane nearly at right
angles to the line of action of the chisel and so formed that the inner and outer surfaces
are parallel to each other for a considerable distance from the cutting extremity sub-
stantially as herein before described and shown.
Dated this Twenty-third day of August 1890.
EDWARD TURNER WHITELOW,
70, Deansgate, Manchester, Agent for the Applicant.