Mechanical drawing self-taught: comprising instructions in the selection and preparation of drawing instruments, elementary instruction in practical mechanical drawing together with examples in simple geometry and elementary mechanism, including screw threads, gear wheels, mechanical motions, engines and boilers (1883)
SCREJV THREADS AND SPIRALS. i5t A Specimen of the form of template for drawingthese curves Is shown In Figure 213 ; g g, Is the cen-tre Hne parallel to the edges R, S; lines m, n, repre-sent the diameter of the thread at the top, and 0, p,that at the bottom or root; edge a Is formed to thepoints… … Fig. 213. to steady it while drawing In the curves. It may benoted, however, that since the curve Is the same belowthe centre line as It is above, the template may be madeto serve for one-half the thread diameter, as at^ whereit Is made from 0 to g, only being turned upside downto draw the other…
Mechanical drawing
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