IMPROVEMENTS IN APPARATUS FOR SCREWING OR TAPPING HOLES IN METAL, PART OF WHICH APPARATUS IS ALSO APPLICABLE TO OTHER PURPOSES
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by George Tosh at the Office of the
Commissioners of Patents on the 18th October 1877. A communication
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from abroad by William Dorward, of Rochester, in the United States of
America.
GEORGE TOSH, of Glasgow, in the County of Lanark, North Britain, Engineer.
'IMPROVEMENTS IN APPARATUS FOR SCREWING OR TAPPING HOLES IN METAL,
PART OF WHICH APPARATUS IS ALSO APPLICABLE TO OTHER PURPOSES." [A
communication from abroad by William Dorward, of Rochester, in the United States
of America.]
This Invention relates to apparatus to be used principally for screwing or tapping
holes in metal, but which is also in part applicable to other purposes, and has for
its object to effect such operations in a simple and more efficient manner than
heretofore, whilst lessening the amount of manual labor and the number of working
parts and consequent expense of the apparatus required.
The improved apparatus comprises a wrench or "dwang" of novel construction
which it is intended to use in combination with a new form of tap for screwing
holes in metal, but which may also be advantageously employed with existing
taps.
The improved wrench, which is of the usual shape in outline, consists of a flat
metal plate with either one or two handles attached to afford the requisite leverage
in turning it. In the centre of the plate there is a diamond or square hole or
opening into which the tap head fits, but instead of this opening being made to admit
only one size of tap, as is usually the case, it is made capable of variation to fit
any size within certain limits, depending on the proportions of the wrench. To
effect this variation an aperture is cut out of the plate, from about the centre to
near one handle, as broad as the necessary strength of the plate will allow, and into
this aperture is fitted a sliding die piece which is adjustable longitudinally by means
of the handle which is screwed into the end of the plate and bears against the die
piece.
The square opening in the centre of the plate is cut partly from the die and
partly out of the plate, with the sides of the square lying at angles of 45 degrees
to the longitudinal centre line of the tool, and with two opposite sides continued
the remaining breadth of the aperture, and when the die piece is adjusted outwards

page_text: from the centre the opening expands and forms a square of increased dimensions.
The opening thus formed bears wholly on two sides of the tap head and on part of
the other two sides, and as it can be adjusted to fit any tap exactly the abrasion or
rounding off of the angular corners of the tap head and the distortion of the die
consequent on the use of imperfectly fitting wrenches are alike avoided.
The tap which I prefer to employ is a screw spindle of the ordinary shape having
four or other convenient number of longitudinal grooves, but whilst in the usual
form the continuity of the raised screw thread which passes round the tap is only
interrupted by the grooves; according to the present Invention the ridge of each
alternate thread on the portions of the tap between the grooves is cut off or
depressed, causing a further intermittent break in the continuity of the screw.
using a tap made in this way it is found that much less labor than usual is required
in turning it to screw or tap holes in the metal, especially in cases where as in "plug
holes the metal is not pierced through.
In
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The wrench and tap may be used in combination, or each may be used separately,
and the wrench alone is obviously applicable for turning wideners for holes, for
fixing or removing nuts, and for any other purposes to which ordinary wrenches or
dwangs are applied, whilst the number of tools required may be considerably
diminished.