Improvements in Cutters for Drilling, Boring, and Tapping Metal.
Year: 1885

page_text: Improvements in Cutters for Drilling, Boring, and Tapping
Metal.
I, LUTHER REYNOLDS FAUGHT of No. 1220 North Eighteenth Street, Phila-
delphia, in the County of Philadelphia, State of Pennsylvania, and United States of
America, mechanical engineer, 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 :-
The object of my invention is to provide a cutter having a series of continuous
cutting blades or wings integral with a central supporting bar and presenting four
or more cutting edges adapted to work at equal distances apart both diametrically
and circumferentially, said cutter being of such transverse section as to possess a
high degree of strength relatively to its sectional area, to afford easy clearance for
chips, and to have its cutting edges so located as to act upon the metal without
the undue friction and loss of useful effect resultant upon a scraping cut thereon.
To this end, my invention, generally stated, consists in a cutter having four or more
continuous ribs or wings projecting from and formed in one piece with a central
bar or core, each of said wings having a cutting edge upon one side of its outer
face and the major part of its thickness located on the opposite side of a plane
which is radial to the axis of the central bar. The improvements claimed are
hereinafter fully set forth.
In the operation of forming holes of circular transverse section in metals,
three classes of tools are employed, to wit: cutters, reamers and drills, each being
suited to a special description of work, the general character of which determines
the kind of tool most appropriately applicable; thus for example, where it is
required to form a circular hole in a solid body of metal, a pointed lip drill working
outwardly from an axial line, must be used, and where holes already formed, as by
coring or otherwise, are to be enlarged and trued out to a circular section, flat
cutters or reamer drills are ordinarily employed, such tools performing their work
on their quter edges, while their central portions are unemployed, otherwise than
as supporting members. Where boring is effected by means of flat cutters, rapidity
and accuracy in the performance of the work is promoted by the application of the
simultaneous action of two or more cutting edges, as by two cutters having four
edges, the distribution of duty between a series of cutting edges enabling a corre-
spondingly quicker feed to be imparted to the cutters, and the division of the strain

page_text: circumferentially upon the metal attaining a closer approximation to absolutely
accurate circular section in the finished hole than would be the case if a single
cutting edge were employed. Cutters of such character are secured in and carried
by a boring bar or stock, which can be either held stationary while the work is
rotated, or be fitted to rotate in the axial line of the hole to be bored, and which
may be supported either at one or both ends, as convenience of operation or the
requirements of the work may dictate. Instances of quadruple edged cutters,
mounted in boring bars as above referred to, are exemplified in Letters Patent of
the United States Nos. 241,481; 253,523 and 302,831, granted and issued to me
under dates of May 17, 1881, February 14, 1882, and July 29, 1884, respectively,
the boring bar in the first and third cases, projecting from a spindle and being
unsupported at the end adjacent to the cutters, and, in the second, being adapted
to be supported at or near each of its ends, by bearings located on opposite sides
of the cutters and the metal upon which they operate.
The above, and other approved constructions of the same general class, are more
particularly intended for and advantageously adaptable to the boring of holes of
diameters sufficiently great to admit of the cutters being mounted in bars of
diameter and strength adequate to resist the torsional and lateral strains which
they sustain in the boring operation, as also to afford a reasonably free escape for
the chips from the edges of the cutters. In holes of comparatively small diameter
bowever, it becomes difficult, if not impracticable, to preserve the desired conditions
of strength and stability in the boring bar, and increased cramping and resistance
to the escape of chips ensues, by reason of the relatively shorter radius of the hole
in the metal to the edge of the cutter acting upon it. My present invention is
specially designed to obviate the practical objections above referred to in the boring
of small holes, while retaining the advantageous features due to the employment of
a series of cutting edges in a tool which is simple and inexpensive in its construction
and effective and durable in operation.
In the accompanying drawings: Figure 1, is a side view, in elevation, of a portion
of a continuous cutter embodying my invention and having a lip drill formed upon
its lower end; Fig. 2, an end view of the same; Fig. 3, a transverse section;
Fig. 4, a side view in elevation, with the lower end ground to proper form for the
use of the tool as a boring cutter, and; Fig. 5, an end view of the cutter when
formed as in Fig. 4.
To carry out my invention I take a bar of steel of any desired convenient length
and forge the same, by hammering it, while hot, between swages or dies, into a
multiple edged cutter, which is in the form of a central bar or stem 1, having four
or more outwardly projecting longitudinal ribs or wings 2, spaced equally around
its axial line, with their outer faces at substantially equal distances therefrom.
The shape and dimensions of the swages employed are such as to produce a cutter,
the transverse section of which, when finished, is clearly exemplified in Fig. 3, its
shape being in accordance with the following general rule. The diameter of the
central bar 1, is equal, as nearly as may be, to one-half the diameter of the circum-
scribing circle of the finished cutter. The number of wings 2, is even (four or
more) and the leading sides of each pair of diametrically opposite wings, that is to
say, those on which the cutting edges are formed, are located on opposite sides of
and at equal distances less than half their thicknesses, from a diameter of the
cutter, so that in lieu of being divided centrally by planes radial to the axis of the
bar, as heretofore, the major portion of the thickness of each wing shall be in rear
of a radial plane which is substantially parallel to its leading side. Further,
while the major portion of the thickness may be increased more or less in the
judgment of the constructor, the minor portion will vary proportionately to
varying diameters of cutters, in each case being regulated to conform to one-half
the thickness necessary to form the drill points hereinafter referred to. By such
arrangement of the metal of the wings, the escape of chips is greatly facilitated,
and the presentation of the cutting edges to the metal operated on, is effected
with greatly decreased tendency to induce a scraping cut thereon. The wings are

page_text: strengthened at their roots by fillets, curved to segments of circles of about one-
fourth the diameter of the circumscribing circle, each of which fillet curves is
tangential to the leading side of one wing and the following side of the next
preceding wing.
After being forged to the form above described, which operation is preferably
performed upon a bar of sufficient length to be divided into a series of separate
and similar cutters, the forged piece is cut into desired lengths, which are finished
by turning or grinding, between centres in their ends, to the required diameter,
and relieving the outer faces from their front towards their rear sides, to afford
proper draft or clearance. The wings may be either parallel throughout their
length to the axis of the cutter, as shown, or may be twisted spirally about the
same, as in twist drills, and while they are preferably continuous throughout the
length of the cutter, a portion or portions of the same may, if desired, be forged to
cylindrical or polygonal form, to enable the cutters to be readily fitted in sockets
or chucks of ordinary construction, and of established sizes.
A cutter forged and finished to the form above described, is adaptable to use as
a drill, a boring cutter, a reamer or a tap, accordingly as its end or the face of its
wings may be dressed to meet the respective requirements of said tools. Figures 1
and 2 illustrate the cutter ground to serve as a lip drill, which presents four
cutting edges 3, for acting upon the outer diameter of the hole where the material
to be removed is greatly in excess of that at the centre, combined with two central
cutting edges 4, which are arranged in proper location to cut easily into the metal.
The drill is formed by first bevelling the wings at the end of the cutter to an angle
of about 30 degrees, and thereafter cutting out two segmental recesses 5, parallel
with the drill lips, said recesses passing completely through the two other wings,
so as to sever the connection of the four wings at the centre, leaving a central drill
point of the desired bevel, from which the recesses 5, afford free passage for the
chips, while the four wings all act as cutters working substantially on the same
plane on the outer diameter. The bevelled edges are ground by the ordinary
processes used for drills, while the recesses 5, may be formed by special round faced
corundum or emery wheels, suitaby arranged for the purpose.
In Figs. 4 and 5, the tool is shown as adapted to use as a boring cutter, in
which case the wings are ground at their ends to inclined faces 6, acting in the
same plane upon the outer diameter of the hole to be bored. It will also be
obvious that the cutters may serve for reamers, and, when properly threaded, for
screw taps, and in such case, possess material advantages over tools of such
character made, as is ordinarily the case, by milling out a solid bar, for the reason
that when worn below standard, they may be enlarged several times by reswaging
and being thereafter tempered and ground to the desired standard, and when so
far reduced that this operation cannot be repeated, they may be forged down to
smaller diameter, one or more times, and used until exhausted. The sharpening
of the tools is effected by grinding continuously off the end, as periodically
required.
The formation of the cutter by forging to the desired form, not only effects a
substantial economy of metal, in avoiding the waste of about one-third of the stock
which would be involved in milling out the spaces between the wings, but also
produces cutting surfaces of better quality and durability, for the reason that the
action of the hammer or dies effects a uniform arrangement of the grain of the
metal around the surfaces of the wings, practically vertically thereto, cross-grained
sections being avoided, and thus the grain being presented under the most favorable
conditions attainable for exerting effective cutting action.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. A forged steel cutter having four or more cutting wings or ribs formed in one
picce with and projecting from a central bar or body, each of said wings having a

page_text: cutting edge upon one side of its outer face and the major portion of its thickness
located upon the opposite side of a plane which is radial to the axis of the bar and
substantially parallel to the front or leading side of the wing, substantially as set
forth.
2. A forged steel cutter having four cutting wings or ribs formed in one piece
with and projecting from a central body, each having an outer cutting edge and
being disposed unequally on opposite sides of a plane radial to the axis of the body,
said cutter having its end bevelled to form two drilling lips, each parallel to the
other and to a segmental recess cut through one of the wings adjacent to its end,
substantially as set forth.