File:Practical engineering drawing and third angle projection, for students in scientific, technical and manual training schools and for draughtsmen (1897) (14781356115).jpg

Identifier: practicalenginee00will (find matches)
Title: Practical engineering drawing and third angle projection, for students in scientific, technical and manual training schools and for ... draughtsmen ..
Year: 1897 (1890s)
Authors: Willson, Frederick Newton, 1855-1939
Subjects: Mechanical drawing Lettering
Publisher: Princeton, N.J., The author
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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n draw first the reference line. Toprovide against overlapping of projectionsthe reference line should be at a greaterdistance below the lowest point, /, of theplan, than the greatest height (a^a^) ofthe end view above x y. Then on MWlay off from 71/ the heights of the vari-ous horizontal edges of the l)lock, derivingthem from the end ^n.ew. Thus OiO, isthe height of A a from M; from 31 tolevel B equals b^b.,, etc. Next project tothe le^-el A fi-om points a a of tlie plan,getting edge ao of the elevation, andsimilarly for all the other corners of theblock. Xofice that all lines that are parallelOil the object icill be parallel in each projec-tion (except when their projections coin-cide) ; also that in the case of sections, thoseonflines iciH be parallel irhich are the inter-section of pen-allcl jjlanes by a third plane.These principles may he ad\-antageously employed as checks on the accuracy of the construction bypoints. The construction of the side elevation is left to the student.
Text Appearing After Image:
146 THEORETICAL AND PRACTICAL GRAPHICS. ^ig-. 2.-^^.

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