A B C OF THE STEEL SQUARE 123 



at B, and also at the center A. This gives the 

 true horizontal trace and major axis. Nbte the 

 size indicated by the arrow lines on the tongue 

 (from heel to B). Transfer the square to the 

 three-ply board (Fig. 82), placing it as shown, 

 with the blade touching A, and the distance of 

 the arrow lines at B. Mark along the inside of 

 the blade of the square and slide the square back 

 until the tongue cuts at A. This gives the minor 

 axis. Now continue this line downwards to 

 guide the position of the square shown at Fig. 

 84. Describe a circle as wide as the rail on the 

 minor axis (Fig. 82). The distance from A 

 (Fig. 84) to the center of the rail is the distance 

 to apply at Fig. 82 for the center of the rail, as 

 this is the point where the center of the rail is 

 fair with the plank. Obtain the width of the 

 face molds, and apply at B and D ; lay the 

 square on the major and minor axis as shown 

 at Fig. 84. Lay a lath on the square, with the 

 point touching the outside of the circle at C; 

 drive in a nail at the heel of the square; shift 

 the lath until the point lies at B, and drive in 

 another nail at the side of the square. This 

 trammel is now ready to sweep the outside of 

 the mold, which is done by reversing the square, 

 as shown by dotted lines. Pull out the nails and 

 repeat the process for the inside of the mold. 



