This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1860 edition. Excerpt: ...as the separate pieces. Thus, hatching parts of a section by black or blue lines may indicate cast or wrought-iron; by yellow or red, brass or gunmetal. Sections of wood are generally hatched as in Fig. 35, by curved lines, imitating somewhat the appearance of the rings seen in timber when cut across. ...
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1860 edition. Excerpt: ...as the separate pieces. Thus, hatching parts of a section by black or blue lines may indicate cast or wrought-iron; by yellow or red, brass or gunmetal. Sections of wood are generally hatched as in Fig. 35, by curved lines, imitating somewhat the appearance of the rings seen in timber when cut across. Two separate pieces of timber seen in cross section, side by side, may be hatched by these lines lying in opposite directions (Fig. 36) Fig. 3S. while timber in longitudinal section may be hatched by crooked Fig. 36. discontinuous lines, lying generally lengthways. In working-drawings--that is to say, projections showing the parts in their proper dimensions, so that a workman can measure and transfer them to the solid material--in such drawings, colours are usefully employed to distinguish the different materials. Thus, parts tinted dark blue might represent cast-iron; while a pale blue might indicate wrought-iron or steel; yellow would mark brass or gun-metal; browuish-yellow, wood; brownish-red, copper; and so on. When any special material is to be used, its name is generally written on such part of the drawing as represents it. Central Lines.--In almost all mechanical works, or at least in their details, there is necessarily symmetry, or repetition of equal parts on different sides of some central points. For instance, a cylinder, cone, column, and such like bodies, are symmetrical round their axes. The teeth of a wheel are symmetrical round its centre, and so with almost all the forms suited to machinery. It is, therefore, most important in mechanical drawings to mark the central or axial lines of the different parts. As these lines do not necessarily appear on the ma terial, they are generally distinguished from those that mark outlines...
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