CLAY WORKING INDUSTRIES. 157 



The front end of' the shaft is equipped with a casting designed to 

 gather up the clay delivered to it by the knives or blades in rear, and 

 force it out of the aperture in front. 



This casting is a solid, chilled iron screw, made in a single thread or 

 double thread according to the kind of bar which is to be produced. 



' The shaft, which is unsupported at its working end, is held firmly in 

 position in two long bearings and is driven by powerful gears, either 

 single or double. The backward thrust of the auger shaft is of course 

 equal to the forward push it gives the clay, and this has to be provided 

 for by a carefully adjusted step or bearing designed to take the continual 

 strain and wear without heating. 



This is a short description of the main points of an auger mill. 

 There is a great variety in use and many which have attained special 

 excellence in securing the maximum out-put with the minimum wear and 

 breakage. 



Auger mills are divided into two distinct grades — those which make 

 a side cut brick and those which make an end cut brick. 



By a side cut brick is meant one which has been cut from a bar of 

 clay whose cross section at right angles to its line of flow is equal to the 

 area of the side or largest plane surface of a brick. 



Similarly an end- cut brick is a section of a bar of clay whose cross 

 section represents the end or smallest plane area of a brick. The mechan- 

 ical problems met in producing these two kinds of bars vary quite widely. 



In a side cut machine the bar of clay produced is about four and a 

 fourth inches high by eight and three-fourths inches wide. A brick repre- 

 sents a section of this bar two and a half inches long. The power required 

 to force clay through so large an area is not great, the back thrust of the 

 auger shaft is not very heavy and the general working of the machine is 

 easy. 



The clay in side cut machines is often carried forward by a double 

 thread instead of a single, and nearly all side cut auger points are double 

 threaded, so that, the clay is simultaneously delivered at the end of the 

 auger in two streams which unite into one bar as they pass out of the die. 



In an end cut machine, the bar of clay produced is about two and a 

 half inches wide by four and a half deep, for common sized brick. 



To force clay at a rapid rate through so small an opening requires 

 the use of great power and great strength in the machine and good 

 arrangements for receiving the back thrust of the auger shaft. 



-The auger is a single threaded one — delivering one stream of clay 



only. 



Some machines are adapted to produce both side cut and end cut 



brick they do it in two ways: 1st. By merely changing dies of a side 



cut machine, inwhich case the volume of clay, delivered by the auger is 

 merely split up into two or three end cut streams instead of one side 

 cut stream. 



