CHAPTER III. 

 THE CYLINDER, CONCAVES AND BEATER. 



T is the function of the cylinder and concaves 

 to loosen the kernels of grain from the straw 

 on which they grew. The ends of the cylin- 

 der teeth travel about a mile a minute so that 

 the grain in going through meets the con- 

 cave teeth with considerable force. The con- 

 cave teeth engage with the cylinder teeth in 

 such a way that the grain heads cannot pass through with- 

 out being broken and the kernels knocked out although the 

 straw is in contact with the cylinder but a fraction of a 

 second. If the teeth be in good condition and a sufficient 

 number of rows of concave teeth be used to suit the work, 

 practically all of the grain will be knocked out. 



Cylinder Teeth. When the cylinder is new or newly re- 

 filled, care should be taken to keep the teeth tight until they 

 become fitted to their holes and firmly seated. The cylinder 

 should be gone over occasionally during the first week, and 

 each tooth driven in hard with a heavy hammer and the 

 nuts tightened. If this be done, ordinarily the teeth will 

 give no further trouble, but if at any time they show a ten- 

 dency to get loose, they should be carefully watched. At 



the factory the teeth are driven in and tightened with a long 



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