FEED MILLS 235 



mills or grinders are made of chilled iron, though tool 

 steel and bronze are used to some extent. 



Chilled iron plates or buhrs vary in shape, the usual 

 form being two flat disks which are provided with ribs 

 or corrugations to carry the grain to the outer edge be- 

 tween the milling surfaces (Fig. 175). The cone buhr is 

 the result of an attempt to increase capacity by increas- 

 ing the surface. 



The steel buhr is made in the shape of a roller with a 

 milled surface. The roller mills as used in flouring mills 



FIG. 175 CHILLED IRON BUHRS 



are not used in preparing feed for stock to any extent. 

 It is stated that the steel buhr has a large capacity, but 

 will fill or clog when damp grain is being ground. 



The duplex buhr has two grinding surfaces. The mov- 

 ing plate moves between two stationary plates (Fig. 178). 



In order to grind ear corn a crusher is often provided to 

 reduce the ears to pieces small enough to be fed to the 

 buhrs. In sweep mills the crushing teeth are made a 

 part of the main buhrs. 



333- Sweep mills. The simple sweep mill consists of 

 two conical buhrs. The inner one remains stationary, 



