GB667634A - Improvements in or relating to drawing instruments - Google Patents

Abstract

667,634. Mathematical drawing-appliances. BRADLER, E. March 7, 1950, No. 5689/50. Class 97 (iii). A drawing instrument comprises a rightangled triangular set-square with an inner opening the sides of which are parallel to the outer edges of the set-square, there being provided along either or both edges 6, 7 at least one numbered linear scale having the zero adjacent the apex 9 and on the outer edge 11 a numbered scale corresponding to at least one of the scales on edges 6, 7, the subdivisions of which are in alignment with the corresponding scale on the edge 6 or 7, with yet another scale for measuring angles, arranged along the inner edge 10 and having its angular centre at the apex 9. There may also be provided on one or both edges 6, 7 a numbered linear scale, the divisions of which have correspondingly numbered divisions marked on the scale of the hypotenuse edge 11. The angular scale on the edge 10 is marked for measurement up to 360 degrees. A further numbered linear scale may be provided on one or both the sides 1, 2, the zero of which occurs intermediate the length of the side. The cross-section of the sides 1, 2, 3 has a maximum thickness occurring at the central longitudinal axis of the side, or alternatively the front and rear faces are plane with thinned edge portions on the front face. The scales on the edges 6, 7 have the zero at a position half the thickness of a pencil point from the apex 9.