Practical mechanical drawing and machine design self taught .. (1907)
Westinghouse, Charles. [from old catalog] · Chicago, F. J. Drake & co. · leaf 18
Fig. 20^—Sand Paper Pencil Sharpener. Pencil Erasers. A pencil eraser or rubbershould be of soft, fine-grained rubber, free fromsand or grit and having no tendency to glaze orsmear the surface of the drawing paper. A pencileraser of the kind shown in Fig. 21 will be foundvery satisfactory for… … Pig. 21—Pencil Rubberor Eraser. Fig. 22—Ink Rubberor Eraser. Ink Erasers. Inked lines should always be re-moved from the drawing by means of a sand-rub-ber, which is known as an ink eraser, but never byscratching the surface of the paper with a knife. As all drawing inks dry rapidly, and should…
Mechanical drawing · Machine design
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