An Improved Tap or Chasing Tool for Cutting Internal Threads in Axle Caps and other similar Female Screw Threads.
Year: 1893

page_text: Date of Application, 23rd Oct., 1893
Complete Specification Left, 23rd July, 1894-Accepted, 1st Sept., 1894
PROVISIONAL SPECIFICATION.
An Improved Tap or Chasing Tool for Cutting Internal Threads in
Axle Caps and other similar Female Screw Threads.
We, WILLIAM HENRY WOODHEAD, and FRANK WOODHEAD, of Whitham's
Forge, Leeds, in the County of York, Axle and Spring Manufacturers, do hereby
declare the nature of this invention to be as follows:-
-
This invention relates to an improved tap or chasing tool for cutting internal
threads in axle caps and other similar female screw threads, and its object is to
provide a tap of simple construction the diameter of which is capable of a limited
adjustment so that the diameter of the thread may be gradually enlarged during
the cutting process or a thread already cut may be increased in diameter.
For this purpose we employ a cylindrical chaser-holder approximately the
diameter of the smallest hole to be cut with a female screw thread and preferably
forming a portion of or projecting from the centre of a lever somewhat similar in
form to an ordinary tapping wrench. This cylindrical chaser-holder has two or
more (say three or four) radial guides in which chasers are fitted and these chasers
are adjusted radially by the conical head of a bolt fitted in a central hole in the
cylindrical holder which bolt may be adjusted longitudinally by a wing nut or its
equivalent fitted upon its screwed shank projecting through the other side of said
lever or wrench. A thin plate is fixed upon the end of the cylindrical holder to
form one end of the said radial guides.
It is only necessary for one of the herein mentioned chasers to be actually a
cutting tool (particularly when the instrument is only designed to enlarge a hole
cut with a female screw thread) as the others may be merely guide threads and not
necessarily adjustable.
Dated this 21st day of October 1893.
DRACUP & NOWELL,
Bradford, Agents.
COMPLETE SPECIFICATION.
An Improved Tap or Chasing Tool for Outting Internal Threads in
Axle Caps and other similar Female Screw Threads.
We, WILLIAM HENRY WOODHEAD, and FRANK WOODHEAD, of Whitham's
Forge, Leeds, in the County of York, Axle and Spring Manufacturers 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 relates to an improved tap or chasing tool for cutting internal
threads in axle caps and other similar female screw threads, and its object is to
provide a short tap of simple construction the diameter of which is capable of a
limited adjustment so that the diameter of the thread may be gradually enlarged
during the cutting process or a thread already cut may be increased in diameter.
For this purpose we employ a cylindrical chaser-holder approximately the
diameter of the smallest hole to be cut with a female screw thread and preferably
forming a portion of, or projecting from, the centre of a lever somewhat similar in
form to an ordinary tapping wrench. This cylindrical chaser-holder has two or
more (say three or four) radial guides in which chasers are fitted and these chasers
1 Drine 977

page_text: are adjusted radially by the conical head of a bolt fitted in a central hole in the
cylindrical holder which bolt may be adjusted longitudinally by a wing nut or its
equivalent fitted upon its screwed shank projecting through the other side of said
lever or wrench. A thin plate is fixed upon the end of the cylindrical holder to
form one end of the said radial guides.
Reference is to be had to the accompanying sheet of drawings forming a part of
this Specification, in which similar letters of reference indicate corresponding parts
in each of the figures.
Figure 1, represents a plan view of the improved tool.
Figure 2, represents a side view of the same.
Figure 3, represents a view of the underside of Figure 1.
Figure 4, represents a cross section of the same.
Figure 5, represents a view of a detail hereinafter referred to.
The central portion A of the lever B has a cylindrical projection C on its under
face and four parallel radial guides D are formed in this projection and the under
face of A. The annular plate F is fixed by the four screws a to the projection and
forms the lower ends of the guides D. A chaser or die E is fitted in each of the
said guides each having a segment of a screw thread cut upon its outer ends e.
These segmental threads are so formed in relation to each other that they form
portions of a complete thread, that is to say, the thread formed upon them is the
same as if the thread had been cut upon a cylinder and the spaces intervening
between the dies afterwards cut away. The inner ends i of the chasers are
inclined to the axis of the tool and a central hole G is formed through the tool in
which the screw bolt H is fitted. The bolt H is provided with a couical head H
and a wing nut J is fitted upon its screwed shank projecting through A. It is
obvious that as the wing nut bears against A screwing it further onto the bolt will
draw the bolt further through A and that this movement of the bolt will cause the
conical head, bearing against the inclined ends of the chasers, to force the chasers
outwards and thus expand the tap. Figure 5, represents a separate view of the
bolt and one of the chasers with the inclined end of the latter bearing upon the
conical head of the bolt.
To reduce the size of the tap the wing nut is screwed back away from A and the
bolt pushed back so as to disengage the conical head from the chasers thus leaving
the latter free to be pushed inwards.
It is only necessary for one of the herein mentioned chasers to be actually a
cutting tool, particularly when three chasers are fitted and the instrument is
designed to enlarge a hole already cut with a female screw thread, as the others
may be merely guide threads and not necessarily adjustable. A groove may be
formed in the chasers as shown by P Figure 3 to increase the cutting edges.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is:
1. An adjustable tap, for cutting or enlarging a female screw thread, having two
or more dies or chasers one or more of which is capable of being adjusted radial, to
enlarge the tap, by means of a central bolt having a conical or wedge shaped
portion arranged to bear against the inner end of the adjustable die or dies,
substantially as herein shown and described.
2. An adjustable tap constructed as herein shown and described and illustrated
in the accompanying drawings.
Dated this
.