SCIENCE OF THRESHING. 15 



cylinder teeth are inserted in sockets in the bars, and 

 are secured by nuts on the inside, or by wedges. The 

 cylinder should be capable of endwise adjustment so 

 that its teeth may be made to run centrally between 

 the teeth of the concave. The cylinder acts as a 

 balance wheel in which is stored power to maintain 

 its speed when an undue amount of straw is permitted 

 to enter. There are usually nine or twelve bars in 

 the cylinder. 



As hitherto indicated, the office of the cylinder is 

 to loosen the kernels from the head. This is accom- 

 plished by the cylinder tooth striking the unthreshed 

 head with sufficient force to jar the kernels loose from 

 their retaining hulls. Therefore the cylinder should 

 run with sufficient speed to entirely free all the 

 kernels and not leave any on the straw. If for any 

 reason the cylinder does not do its work thoroughly, 

 the result is wasted grain. In some instances some 

 of the kernels will be partially loosened, but adhere 

 to the head until nearly through the machine, when 

 they will fall out and be carried along with the straw 

 to the straw stack, thus making the machine appear 

 to be at fault in separation by wasting the grain, 

 when in reality the threshing members are not doing 

 their work properly. The usual speed of ordinary 

 cylinder teeth is about 6,000 ft. per minute. Under 

 ordinary circumstances, this will thoroughly dislodge 

 the kernels, if the teeth be brought in contact prop- 

 erly with the heads. In dry, brittle grain, a slower 

 speed may often be used by running the machine 



