CLAYS OF NEW YOKK 



663 



charged into the machine, from which it is forced in the form of 

 a rectangular bar whose cross-section has the same area as the 

 greatest plane surface, or the end of the brick. The bar of clay as it 

 issues from the machine is received on the cutting table, and either 

 is cut up into brick by means of a series of parallel wires set 

 in a frame which slides across the cutting table, in which case the 

 machine stops when the bar has issued a certain length, or the 

 bar of clay issues continuously, and is cut up by means of wires on a 

 revolving frame. 



The plunge machine consists of a large iron cylinder into which 

 the clay is charged. From this it is forced out through the die. 



The auger machine consists of a cylinder with a conical end. In 

 this is a horizontal shaft bearing a screw or knife blades so set that 

 their action will force the clay forward. At the forward end of the 

 shaft is an iron screw which forces the clay out through the die. 

 The clay is fed at the large end of the cylinder. It will thus be 

 seen that the clay undergoes a large amount of compression and 

 that considerable power is required to force it through the die. 



Auger machines are either end-cut or side-cut, depending on 

 whether the area of the cross-section of the bar of clay corresponds 

 to the end or side of a brick; and consequently the mouthpieces 

 vary in size and shape of cross-section, according to the kind of 

 brick or other product to be turned out. 



Mouthpieces are generally made of steel, are steam-heated, and, 

 in order to prevent the formation of a serrated edge on the emerg- 

 ing bar of clay, much attention is given to the internal shape of the 

 die. When a bar of clay emerges f ro^m a rectangTilar opening, there 

 i8 more friction at the comers than in the center of the bar or on 

 the sides, and for this reason the internal form of the mouth- 

 piece should be such that a sufficient quantity of clay will be forced 

 toward the corner of the die to preserve an equal velocity in all 

 portions of the emerging clay stream. At times the mouthpieces 

 or dies are watered or oiled in order to facilitate the issuance of the 

 clay. The practice of steam-heating the die is rather an American 

 one. 



