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BELL SYSTEM TECHNICAL JOURNAL 



is one third that of the water ram, so that the pressure on the lead dur- 

 ing extrusion is about 54,000 pounds per square inch. 



Aside from increasing output many studies have been made to 

 determine the exact mechanism of lead extrusion, the relative flow of 

 lead in different parts of the extrusion block, the effect of application 

 of heat at different points, etc. 



Fig. 19 — Delivery of empty reels from yard 



An interesting experiment consisted in filling an extrusion block with 

 layers of different colored waxes and noting their flow under pressure. 

 This gave valuable data as to the proper contour of the extrusion 

 chamber. 



The concentricity of sheath is affected not only by the contour of 

 the extrusion chamber but also by the manner in which heat is applied ; 

 and thickness is affected by temperature and speed of extrusion so that 

 the human element is an important factor, and it is necessary to have 

 thoroughly trained and reliable operators on this kind of work. Tem- 

 perature indicators are used to show die block temperatures and the 

 temperature of the molten lead is automatically controlled and recorded. 



