Page:Popular Science Monthly Volume 91.djvu/785

 Simple Designs for Sheet Metal Working

��VI. — Method of developing patterns for elbows of various shapes By Arthur F. Payne

Director of Vocational Education

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��O the students who have been follow- ing and working out the problems in this series of articles, the six elbows drawn and described will be simple to develop. The first three — the square, oblong and oval elbows — are in common

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'," — Pattern

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��everyday use. The others are more uncommon, and are used in special cases for special pur- poses. These will make good exhibit pieces to place in shop windows as a proof of ability to develop and make unusual pieces. The patterns for all of these six elbows are developed

��torn B. It will be necessary to develop the pattern for one piece of the elbow, the same as in the round elbow. In this case the pattern is developed for the part marked A. The seam is indicated in the center of the short side of the elbow (see bottom view B). Moving clockwise around the bottom view, number each point I, 2, 3, 4, 5 and 6 as shown. Lay off the base line C-D, finding the correct length by taking the distance 1 to 2, 2 to 3, 3 to 4, 4 to 5 and 5 to 6, from the bottom view B. Run these points up- ward from the base line as indicated by the faint lines, then from the joint line project

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��The square, the oblong and the oval elbows are in common everyday use and the method for their development is exactly the same as that for making the pattern for the ordinary round elbow

��in exactly the same way as the pattern for the ordinary round elbow illustrated in the first article of the series (June, 191 7, issue). The square elbow, Fig. 1, is the simplest to make. First, draw a front view of the elbow shown at A and then draw the bot-

��the points of intersection to the pattern, marking each point with a cross where it intersects the similarly numbered line com- ing up from the base line C-D. Connect these crosses with straight lines and the result will be the pattern as shown. Allow-

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