Improvements in screw taps
Year: 1899

page_text: I, HANS OSKAR NIENSTAEDT, of Dronning Olgas Vej, Copenhagen, Denmark,
Mechanical Engineer, do hereby declare the nature of this invention to be
follows:
-
This invention relates to screw taps of a type in which the taps are provided
with both side and end cutters.
In my former Patent No. 19,493, 13th September 1898, entitled "Improvements
in screw taps" I described taps with helically shaped side and end cutters and
in which the end cutters had the shape of those of a twist drill and in which the
angle of the end cutting edges was the same in each of a set of taps.
I have discovered that in practice by giving the end cutting edges of a series
of taps different angles varying from an acute angle in the first of a series to obtuse
in the last of the series, the end cutter of the intermediate tap being about right
angled, that holes perceptibly smaller in diameter than the taps may not only
be enlarged and threaded but threaded to the bottom of the hole. I have further
discovered that by giving the side cutting edges an angle of forty-five degrees
or thereabouts a cleaner cut may be made with less labour than by the ordinary
taps with side cutting edges made right angled or thereabouts.
My present invention differs from that herein before referred to in that I
make a series of taps with end cutting edges of different angles and the whole
of the series with side cutting edges of an angle of forty-five degrees or there-
about.
I, HANS OSKAR NIENSTAEDT, of Dronning Olgas Vej, Copenhagen, Denmark,
Mechanical Engineer, 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 consists of a screw tap with two or more cutters, the side edges

page_text: of which are shaped helically; and the lower end is made in the shape of the
point of a twist-drill.
Fig. 1 shows a taper tap.
Fig. 1 is a plan of same looking upward.
Fig. 2 shows an intermediate tap.
Fig. 2 is a plan of same looking upward.
Fig. 3 shows a finishing tap.
Fig. 3 is a plan of same looking upward.
Fig. 4 is a cross section through one of the taps.
In my former Patent No. 19,493, dated the 13th day of September 1898,
entitled "
Improvements in screw taps" I described taps with helically shaped
side and end cutters in which the end cutters had the shape of those of a twist
drill and in which the angle of the end cutting edges was the same in each of a
set of taps.
I have discovered, that in practice by giving the end cutting edges a, a
of a series of taps different angles varying from an acute angle in the first
(Figure 1) of the series to obtuse in the last (Figure 3) of the series, the end
cutter of the intermediate tap (Figure 2) being about right angled, that holes
perceptibly smaller in diameter than the taps may not only be enlarged and
threaded but threaded to nearly the bottom of the hole. I have further dis-
covered that by giving the side cutting edges bb an angle of forty-five degrees
or thereabouts (see Figure 4) a cleaner cut may be made with less labour than
by the ordinary taps with side cutting edges made right angled or thereabouts.
My present invention differs from that herein before referred to in that I make
a series of taps with end cutting edges of different angles and the whole of the
series with side cutting edges bb of an angle of forty-five degrees or thereabout.
The form I give my side and end-cutters allows of the grinding of the cutting
edges when they get dull without diminishing the diameter of the tap.
In Figures 1, 2 and 3 the lines a a of the end cutting edges are produced by
dotted lines until they meet in order to more clearly indicate the angles of the
respective end cutters.
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. The combination of three taps forming a set having twist-drill-shaped end
cutters each with a cutting edge of a different angle substantially as set forth.
2. The combination of three taps forming a set the taper tap having acute-
angled end cutters the intermediate tap having end cutters of a more obtuse
angle and the finishing tap having end cutters of a still more obtuse angle sub-
stantially as set forth.
3. In screw-taps, side cutters with cutting edges forming an angle of about
forty-five degrees with the centre line of the tap, substantially as set forth.
A. The specific combination of three taps shaped as shown in the drawings.
Dated this 12th day of September 1900