usb encryption 15.5 download

LINING-IN DRAWINGS IN INK 33. ALTHOUGH the student, up to the present stage in his study, has not been called upon to draw anything to scale which necessitates a greater amount of exactness in the use of his pencil and instruments than he may yet have exercised he should still have acquired a sufficient ability in their manipulation to enable him to put in fairly sound and fine lines when necessary. But as the permanence and practical use of a drawing especially one of any engineering subject are matters of necessity and great importance, it must be committed to paper in a better medium for its preservation than that offered by the use of plumbago. The lead-pencil is only employed for the rapid committal to the paper of the ideas embodied in the drawing, but for the preser- vation of these, and for constructive purposes, the design must be fixed in some coloured pigment or ink. As previously stated at the commencement of this work, China or India ink is the special pigment used by the mechanical draughtsman for this purpose, and it is now intended to explain the proper application of the different kinds of lines used in inking or lining-in an outline mechanical drawing. We may state at the outset in this part of our subject that in what are known as ordinary, workshop, or " shop drawings," only one kind of line is used in inking them in, and that is a firm, sound, black line, about -fa of an inch in thickness. In all good modern workshops, no workman is allowed to decide by measurement with his rule the dimen- sions of any part of a piece of mechanism shown on a drawing, as all such parts are, or should be, dimensioned with figures on the drawing itself before it leaves the drawing office. But for the purposes served by a drawing in outline, or one not intended for shop use, different thick-