PRECISION TOOL MAKING 395 



Making Die Blocks for Sheathing Lead-Covered Cable 



The making of the die blocks used in the hydraulic presses for 

 sheathing lead-covered cable is of interest on account of the method 

 used. The milling of the die contour, which is irregular in shape, is 

 done on a die sinking machine shown in Fig. 22, the upper die being 



Fig. 22 — Milling on die sinking machine the contour of die block for 

 sheathing lead-covered cable 



the master and the lower the die being profiled. The principle of the 

 machine is that of having the cutter or milling tool automatically con- 

 trolled and guided by means of a very sensitive tracer, which follows 

 the contour of the master. This is accomplished by having individual 

 motor drives and electrically operated clutches for each of the feeds, 

 which are controlled by the movement of the tracer making and 

 breaking the electrical circuits as it comes in contact with the surface 

 of the master. This results in the feeds operating to move the table 

 holding the dies and the slide holding the tracer and the cutting tool 

 in such a manner that the tracer will follow the outline of the master 

 die. The milling out of the opening is done by a series of either 

 horizontal or vertical cuts, the machine automatically reversing at the 



