Simple Designs for Siieet Metal Working 



XII. — Interesting pattern problems 

 developed by means of radial lines 



By Arthur F. Payne 



Director of Vocational Eklucation, Johnstown, Pa. 



IN the last issue, one of the problems 

 developed was the pattern for the hole 

 in the shield of a hopper. The illus- 

 tration Fig. 1 shows the method of de- 

 veloping the shield for a "jack pipe" or 

 bath room ventilator pipe coming through 

 a roof, (in the illustration the roof is 

 drawn very small). The method used is 

 exactly the same as for the hopper, but 

 as the hopper was developed by radial 

 lines and this jack pipe is developed by use 

 of parallel lines, it will make it much 

 easier and make a good review of the 

 method if we briefly outline the steps of 

 the development. 



First, draw the side view A, Fig. 1, 

 obtaining the angle of the shield from the 

 pitch of the roof as described in the last 

 issue. Second, draw the bottom view B. 

 Third, project the lines from the points on 



Patter r\ 

 Kandle 



hole, also that if we can get the correct 

 widths on these lines we shall have the 

 pattern of the hole. To get these correct 

 widths we must draw the front view G, 

 which is done as follows: Fifth, draw the 

 pipe and the bottom view being careful 

 to note that the numbers are turned a 

 quarter turn to the left, number one 

 being in front instead of on the right side. 

 Sixth, project the lines up from the bot- 

 tom view until they cross the same 

 numbered lines coming over from the side 

 view. Mark these points with a cross. 

 Connect these crosses with a curve and 





Developing a pattern to make a shield for a jack 

 pipe and also a pattern for making a liquid measure 



the bottom view circle upward until they 

 meet the shield line C-D. Fourth, pro- 

 ject lines out exactly at right angles to 

 the shield line C-D. Draw the center 

 line E-F Now it will easily be seen 

 that these lines give us the length of the 



we will have a correct view of the front 

 view of the joint of the pipe and the 

 shield. The upper part of the joint is 

 drawn in dotted lines because it is back 

 of the pipe and cannot be seen. Seventh, 

 with a pair of compasses measure the 



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