THE CYUNDER, CONCAVES AND BEATER l6l 



damp grain six rows will be necessary. Rye can usually 

 be threshed with two rows, but the cylinder speed should 

 be 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 too many teeth are used, or when they are left higher 

 than is necessary, the straw will be cut up, the grain may 

 be cracked and, besides 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, Tur- 

 key 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 



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