THE CYLINDER, CONCAVES AND BEATER. 137 



higher than for wheat. Oats when dry can generally be 

 threshed with two rows of teeth, but flax and timothy will 

 require six rows. Where four are used, they are most 

 effective if one concave be placed clear back and one in front 

 with a blank in the center. In hand feeding, if the straw 

 be dry and brittle, the cylinder can be given more "draw" 

 by placing a blank in front. Always use as few teeth, and 

 leave them as low as is possible and thresh clean. When 

 more teeth than are required are used, or when they are left 

 higher than is necessary, the straw will be cut up, and, be- 

 sides using more power, the separation is made much more 

 difficult, and the sieves are obliged to handle an unnecessarily 

 large amount of chopped straw. It is better to use two rows 

 set clear up, than four rows left low. Sometimes a row of 

 teeth is taken out of a concave, making it possible to use 

 one, three or five rows. 



Special Concaves. Some grains, as for example, Turkey 

 wheat, are extremely difficult to thresh from the head, and 

 if it be found that the regular six rows will not thresh clean, 

 a three-row concave, filled with corrugated teeth, should be 

 procured. This, with two regular concaves, will give seven 

 rows of teeth. Should it be necessary, two, or even three, 

 three-row concaves of corrugated teeth may be used. The 

 three-row concaves of corrugated teeth are usually used for 

 threshing alfalfa, but for clover, the special clover concaves 

 are necessary. Information concerning them is given else- 

 where in this book. 



