Improvements in Set Squares.
Year: 1892

page_text: Date of Application, 16th Nov., 1892
Complete Specification Left, 19th Jan., 1893-Accepted. 25th Mar. 1893
PROVISIONAL SPECIFICATION.
Improvements in Set Squares.
JOHN MITTON, 9 Marsden Street, Chorlton-upon-Medlock, Manchester,
Engineer's Draughtsman, do hereby declare the nature of this invention to be as
follows:-
This invention relates to set squares used by draughtsmen & others, & consists
of certain improvements, whereby any angle or taper can be readily obtained or
measured with the use of one set square only.
From any of the three points of the set square, at any convenient radius I form a
shallow circular dovetailed groove, & in the groove I place a sliding circular are
f
graduated on the edges with degrees, tapers per foot, or other graduations, there
being datum lines on the body of the square.
To use the set square for any angle different to the angle of the set square itself,
the circular arc is turned in its groove sufficient to place the desired angle or
taper indicated on the graduated arc, opposite a datum line marked on the body of
the square.
The corner from which the circular groove is struck, & the end of the sliding
circular arc form the base of the set square.
Dated this Twelfth day of November 1809
COMPLETE SPECIFICATION.
Improvements in Set Squares.
I, JOHN MITTON, 9, Marsden Street, Chorlton-upon-Medlock, Manchester,
Engineer's Draughtsman 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 set-squares used by draughtsmen and others, and consists
of certain improvements whereby any angle or taper can be readily obtained or
measured with the use of one set-square only, thus forming a set-square and a
protractor combined.
From a centre at or near any of the three points of the set square with any
convenient radius, I form a shallow circular dovetailed groove A. and in the groove
I place a sliding circular arc B.
The circular arc B. is graduated on the edges with degrees, tapers per foot, or
other graduations, there being datum lines C on the body of the set-square.
If required the body of the set-square is conveniently graduated D. and datum
lines E. placed on the circular arc B.
When the centre of the radius of the circular arc and groove is at a point of the
set-square, the point is left square (or at whatever angle it may be), but when the
aforementioned centre is near a point, the point is made circular, as at G, with a
radius struck from the same centre as the circular groove and arc are struck as
illustrated in the annexed drawing.
The latter method makes a very durable point but is costly of manufacture.
The former method is cheaper of manufacture but not so durable, as a sharp
corner would be liable to loose its point and when in use would then, oscillate on a
false centre.
To obviate this defect I would form a firm point by inserting a metallic plate or
plates in the corner of the set-square.

page_text: To use the set-square for any angle or taper different to the angle of the set-
square itself, the circular arc is turned in its groove in the direction shewn at F
sufficient to place the desired angle or taper indicated on the graduated arc B
(or set-square. D) opposite a datum line marked on the set-square C (or circular
arc E.
The corner G, and the end of the circular are B forming the base of the set-square,
thus obtaining any desired angle or taper.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
A set-square with a circular dovetailed groove formed in the body of it, which
groove contains a sliding circular graduated arc used for obtaining any desired angle
or taper in the manner substantially as hereinbefore described and illustrated in the
drawing hereto annexed.
Dated this 18th day of January 1893.
JOHN MITTON,
9, Marsden Street, Chorlton-upon-Medlock, Manchester