The Sheet metal worker's instructor : for zinc, sheet iron, copper, and tin plate workers, and others, containing a selection of geometrical problems, also practical and simple rules for describing the various patterns required in the different branches of the above trades (1906)
Warn, Reuben Henry · Philadelphia : Henry Carey Baird & Co. · leaf 233
160' instrument for measuring angles in drawings, etc. Let A B be the base line, from which, ascends a Hne c e. If we apply the lower straight edge of the instrument to the former line, and bring the small nick or mark in the … centre of its straight side to c, wo shall find that the line EDO cuts the circumference of the protractor at 90°; e c b is, therefore, an angle of 90°, or a right angle. Similarly F c a is an angle of 45°, or half a right angle, and Fig. 40. G c B is an angle of 60° (the mark ° indicates a degree…
Sheet-metal work
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
