Self-help mechanical drawing; an educational treatise by Hawkins Nehemiah 1833-

Author:Hawkins, Nehemiah, 1833- [from old catalog]
Language: eng
Format: epub, pdf
Tags: Mechanical drawing
Publisher: New York, T. Audel & co
Published: 1914-03-25T05:00:00+00:00

Hawkins' Mechanical Drawing.

163

A

B

Fig- 233

Fig- 235.

Hawkins' Mechanical Drawing.

wheel, taking on the compasses a radius equal to the pitch of the tooth; set them on the pitch line at the point G, already spaced for thickness of tooth, draw line // from pitch line to root of tooth ; proceed similarly all around the circle, completing one side. Next, reverse the operation and draw the corresponding side of the root of tooth. Now take a radius equal to half the space between teeth and the thickness of tooth on pitch line, and, with center in pitch line, as shown at /. draw the outside or addendum of tooth,/; it will be apparent that the reverse addendum of the tooth next adjoining can be formed at the same time, with one setting of the compasses; finish all the teeth similarly; the front elevation will thus be completed.

Fig. 233 is an excellent example of sectional drawing, to be executed as follows:

First draw the center line L M oi fig. 233, lay off

at each side of it half the breadth of face and of the hub; now project, from center line CD, in the front elevation, fig. 234, with the T-square the upper and lower teeth, the fillets, the chamfers, the hub and center hole, also dot in the pitch line FF, take the radii and draw the fillets and chamfers; draw section lines and the view will appear as shown in fig. 233.

Fig- 235 is a side elevation of fig. 234, and is a fine sample of projection, to be executed as follows :

Proceed similarly as for fig. 233, projecting the lines from the outside edges of the front elevation, instead of from the center line (7 Z> as in last figure, and the end elevation will be as shown in fig. 235.

The student will be assisted in understanding this working drawing by consulting the pages under the heading of " Gearing."

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