Improvements in the Construction of Taps for Cutting Internal Screw Threads.
Year: 1894

page_text: Date of Application, 19th Mar., 1894
Complete Specification Left, 18th Dec., 1894-Accepted, 19th Jan., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Taps for Cutting Internal
Screw Threads.
We WILDSMITH BADGER of 12 Wilton Square, New North Road, London, N.
Mechanical Engineer and HENRY BADGER of 13 Petworth Street, Battersea,
Record Searcher do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in the construction of taps for cutting
internal screw threads.
According to our invention we construct the said taps with only one line of
cutting edge said cutting edge being parallel to the axis of the tap or angular or
spiral in regard to same as preferred, and we so relieve or reduce the diameter of
the screw thread of the tap at suitable parts as that the latter will take a bearing
in the hole being tapped upon (preferably) three lines of contact, said lines of
contact being so arranged and situated as to keep the said single cutting edge
well up to its work when the tap is rotated. We prefer to arrange one line of
contact about opposite to the cutting edge, the second in the rear of the cutting
edge and about midway between the same and the first mentioned line of contact,
whilst the third line of contact is constituted by the cutting edge itself and that
portion of the tap immediately behind the same. If desired the number of the
said lines of contact might be increased but we prefer to employ three as above
set forth.
Dated this 19th day of March 1894.
Improvements in the Construction of Taps for Cutting Internal.
Screw Threads.
We, WILDSMITH BADGER, of 12 Wilton Square, New North Road, London, N.,
Mechanical Engineer, and HENRY BADGER of 13 Petworth Street, Battersea,
Record Searcher, 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 improvements in the construction of taps for cutting
internal screw threads.
According to our invention we construct the said taps with only one line of
cutting edge, in lieu of with several lines of cutting edge as heretofore, said single
cutting edge being either parallel to the axis of the tap, or angular or spiral in
regard to the same, as preferred, and we so relieve or reduce the diameter of the
body of the tap at suitable parts as that the latter will take a bearing in the hole
being tapped upon (preferably) three lines of contact, said lines of contact being
so arranged and situated as to keep the said single cutting edge well up to its work
Price8d1

page_text: when the tap is rotated. We prefer to arrange one line of contact about opposite
to the cutting edge, the second in the rear of the cutting edge and about midway
between the same and the first mentioned line of contact, whilst the third lice of
contact is constituted by the cutting edge itself and that portion of the body of the
tap immediately behind the same. If desired the number of the said lines of
contact may be increased, but we prefer to employ three only as above set forth.
In the accompanying drawings in which similar letters refer to corresponding
parts in all the figures :-
Figs. 1 and 2 represent in elevation and transverse section respectively a screw
tap constructed in accordance with our invention..
Fig. 3 is a sectional elevation on line 1-2 Fig. 5 of a screw tap constructed in
accordance with our invention and provided with an adjustable chaser blade.
Fig. 4 is an elevation at right angles to Fig. 3, and Fig. 5 is a transverse section
of Fig. 4.
a is the body of the tap, and b is the single cutting edge thereof. The body a
is reduced in diameter at suitable parts so as to take a bearing in the hole being
tapped upon three lines of contact c c c², as shewn clearly in Figs. 2 and 5 where
the dotted circles indicate a hole being tapped. The line of contact c is constituted
by the cutting edge b and that portion of the tap body immediately behind the
same, the line of contact c³ is about opposite the cutting edge b, and the line of
contact c¹ is situated about midway between c and c². The above arrangement
keeps the cutting edge well up to its work when the tap is rotated.
al, Figs. 3, 4 and 5, is an adjustable chaser blade having teeth or serrations
formed on the edge thereof to correspond with the pitch of the screw thread on the
body a, said chaser blade a¹ fitting within a groove d formed in the body a and
being kept from slipping out of the same by convenient set screws e. It will be
seen ou referring to Fig. 3 that the chaser blade a¹ is wedge shaped and that
behind the same in the grooved there is disposed a wedge piece by the longi-
tudinal movement of which the lateral adjustment of the chaser blade a is effected.
This longitudinal movement of the wedge piece f is in turn effected by means of
the adjusting screw spindle g which passes down the interior of the tap and bears
upon the wedge piece f. By the above described arrangement the chaser blade
when worn may be adjusted laterally to a nicety.
It will be obvious that by dispensing with a screw thread on the body a and
with serrations on the chaser blade a' the tool will serve as a reamer.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. A tap for cutting internal screw threads, consisting of a body a constructed
with but a single cutting edge band so shaped in transverse section as to take a
bearing in the hole being tapped upon three or more (but preferably three) lines
of contact, substantially as described and illustrated.
2. A tap for cutting internal screw threads constructed as set forth in the
preceding claim, and provided with an adjustable chaser blade a' arranged and
adjusted substantially as described with reference to and illustrated in Figs. 3, 4
and 5 of the annexed drawings.
3. The general construction and arrangement of taps for cutting internal screw
threads, substantially as described with reference to and illustrated in the annexed
drawings.
Dated this 18th day of December A.D. 1894.
E. P. ALEXANDER & SON,
Chartered Patent Agents,
19, Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicants.