IMPROVEMENTS IN AND RELATING TO SCREW-TAPS
Year: 1883

page_text: LETTERS PATENT to Henry Harris Lake of the firm of Haseltine Lake
& Co Patent Agents Southampton Buildings London for an Invention of
"IMPROVEMENTS IN AND RELATING TO SCREW-TAPS" Communicated to him
from abroad by Cicero Rodney Crane French and Frank Bullivant both of
Providence, Rhode Island, United States of America, Machinists
PROVISIONAL SPECIFICATION left by the said Henry Harris Lake at the
Office of the Commissioners of Patents on the 15th January 1883.
"
HENRY HARRIS LAKE of the firm of Haseltine, Lake and Co Patent Agents,
Southampton Buildings, London, "IMPROVEMENTS IN AND RELATING TO SCREW-
TAPS [A communication to him from abroad by Cicero Rodney Crane French
and Frank Bullivant both of Providence, Rhode Island, United States of America,
Machinists]
The object of this invention is to construct a screw-tap which can be adjusted
so as to compensate for the usual diminution in size resulting from wear, and
which can be made perfectly parallel in its length, or tapering in either direction
as may be desired
According to the said invention the body of the tap, is provided with a longi-
tudinaly cut or slot which extends through the threaded or cutting part of the
said tap, and, when two sets of screws, as hereinafter described, are to be used the
cut should extend well up into the shank. A set screw is put through the tap
transversely to the said cut to draw the two sides of the tap together; tho said
screw being fitted loosely into one part of the tap and with a screw-thread into
the other part
Two taper screws are fitted into two taper holes intersecting the said cut or slot
on opposite sides of the tap and near its cutting end, so that when the said taper
screws are turned inwards, the two parts of the tap are spread apart
If preferred, a longer taper screw may be inserted in the end of the tap in line
with the axis thereof, in lieu of the said two screws; Or the said two screws may
be put in the end of the tap, one on each side of the centre.

page_text: The use of two screws, either in the side or end of the tap, is preferable to the
one central screw as there is a tendency in the two parts of the tap to twist or
rock on the centre screw which is not the case when two screws are used
To further improve the tap by keeping its two sides parallel and thus securing
the integrity of the pitch of the thread, a second set-screw and two more taper
screws are placed at, or near, the upper end of the threaded part of the tap in the
same manner as those herein before described. In the place of each pair of taper
screws one taper screw screwed throughout its whole length and long enough to
reach through the tap may be used: these screws operate in a like manner and
produce the same effects as the shorter ones.
In operation, if a new tap does not come up to the required size when tempered,
or if an old tap has become somewhat worn by use, by loosening the set-screws
and turning in the taper screws the tap may be expanded or vice versa, if it is too
large. By operating the set of screws at one end of the tap, to the exclusion
of the set at the other end, the tap may be made to taper slightly in either
direction

page_text: Having thus fully described the said invention as communicated to me by my
foreign Correspondents and the manner of performing the same I wish it understood
that I Claim -
"
First. A screw-tap slotted as described, and provided with the set-screw a and
the short taper screws b, b, substantially as set forth.
Second. A screw-tap slotted as described and provided with the set-screw a and
taper screw b¹l.
Third. The combination, with a slotted screw-tap having the set-screw a and
the taper screws b, b or b¹¹, of the set-screw a' and two short taper screws b1, b¹ or
one long taper screw b¹¹¹.
Fourth. A screw-tap having a longitudinal slot extending through its threaded
or cutting portion into the shank, and provided with means for expanding or
contracting the two parts of the tap, substantially as described.
In witness whereof I the said Henry. Harris Lake have hereunto set my
hand and seal this Tenth day of July in the year of our Lord One thousand
eight hundred and eighty three.
HENRY H LAKE. (1.8)