Simple Designs for Sheet Metal Working 



VII. — Development of patterns for tee-joints of various angles 

 By Arthur F. Payne 



Former Director of Vocational Education at Columbia University 



TO those who have followed this series 

 of articles, the new elements in the 

 development of patterns to be con- 

 sidered now will be easily mastered. The 

 tee-joint made of square pipe, as shown in 

 Fig. i, was chosen to illustrate this prob- 

 lem, because it is much easier than the tee- 

 joint made from round pipe, although the 

 method used is 

 the same in both 

 cases. 



To develop 

 the pattern for 

 the square tee- 



Seam 



Fig. I 

 Square 90° 



Seam 



The manner of laying out the lines in making 

 a draft for a ninety - degree square pipe 



joint having an angle of 90 deg., first 

 draw the front view A. Be very careful 

 and do not confuse the diagonal size of the 

 pipe with the square size. It is best to 

 make sure of this by drawing the end view 

 B the size wanted; then project the sizes to 

 the front view, and draw the bottom view 

 C. Number the corners from 1 to 5 as 

 shown. To develop the pattern for the 

 vertical pipe, draw the base line D-E and 

 find the length of this base line by laying off 

 the distances between the numbered corners 

 on the bottom view C. Draw lines up- 

 wards from these points on the base line. 

 Project corner 1 and 5 on the bottom view 

 upward until the line strikes the bottom of 

 the horizontal pipe; then run the line over 

 to the right until it crosses the lines 1 and 5 

 coming up from the base line D-E. Make 

 a cross where the same numbered lines cross 

 each other, and run up and over corners 3, 

 2 and 4 from the bottom view and over to 

 the right until they intersect the similarly 



numbered lines coming up from the bottom 

 view. Connect the crosses with straight 

 lines and you have developed the pattern 

 for the vertical pipe. 



To develop the pattern for the horizontal 

 pipe, number the corners of the pipe, as 

 shown in the end view F; project upwards 

 the width of the pipe and lay off the correct 

 length on the line H-K by stepping off the 

 distance between the numbered corners of 

 the end view. To develop the pattern for 

 the hole G, project point 2 of the end view 

 over to the front view until it strikes the 

 joint line, then go upward until it crosses 

 the line 2 coming up from the line H-K, 

 and make a cross where the lines come to- 

 gether. Do the same with points 4 and 3. 

 Connect the crosses with straight lines and 

 you will have the pattern for the horizontal 

 pipe. 



The hole G in this pattern will have to be 

 cut out with a chisel or a hollow punch. 

 Some metal workers object to this and 

 prefer to have one half of the hole on each 

 edge where it can be easily cut out with a 

 pair of snips. The dotted lines on the pat- 

 tern show where the hole would be in this 

 case. To develop the pattern with the 

 hole on the edges, simply mark the seam at 



Fiq.2 

 • Square45 



Y 4 rii 



uii 



A square pipe pattern of forty-five degrees 

 is developed like one of ninety degrees 



the bottom of the pipe at 3 and number it 1 

 instead of 3. 



To develop the patterns for the square 



939 



