SOME CERAMIC MANUFACTURING DEVELOPMENTS 261 



chamfered the ends. The finished core was then removed from the 

 mandrel, dried and fired. This method of manufacture produced 

 cores of superior quaHty at a greatly reduced cost. 



Porcelain Protector Blocks 



The next major development was that of the manufacture of pro- 

 tector blocks. These small porcelain blocks, used in open space cut 

 outs and shown in Fig. 3, are illustrative of parts where it was necessary 



Fig. 3 — Porcelain protector blocks. 



to undertake manufacture for quality considerations and where such 

 manufacture resulted in cost reduction. They were originally pur- 

 chased from domestic sources which were unable to meet consistently, 

 required limits as close as +. 020-inch and —.015-inch on a .390-inch 

 dimension. The dimensional deviations encountered necessitated 

 sorting to insure proper functioning in the field, and it was necessary 

 to scrap a large percentage of the purchased parts. Difficulties were 

 also experienced in the assembly of the blocks because of manufacturing 

 defects such as small fins and low strength. 



Common commercial practice on most porcelain parts of this 

 type at that time was to form the parts on a hand screw press, re- 

 move fins by hand, and fire the blocks in refractory containers in 

 intermittent furnaces. The amount of hand labor involved was 

 large and early studies of the economics of manufacture showed 

 it would be necessary to develop new methods of manufacture before 



