164 SCIENCE OF SUCCESSFUL THRESHING. 



beans, while its capacity is much, greater. In changing to 

 the special cylinder, it is necessary to procure the special 

 concaves and concave-circles, as well as the cylinder. 



Threshing Rice. This grain is difficult to thresh clean 

 from the heads without cracking or hulling the kernels. 

 The teeth in a regular cylinder are spaced too closely for 

 ordinary rice threshing, although good work is sometimes 

 done when the teeth have become somewhat worn and are 

 consequently thinner than when new. The "Case" rice 

 thresher has the proper spacing of teeth to thresh this 

 grain out of the heads without cracking more than a small 

 percentage. What is said in Chapter III in regard to the 

 proper endwise adjustment of the cylinder and the necessity 

 of keeping the teeth straight applies particularly to rice 

 threshing. In reading that chapter with reference to rice, 

 however, it should be born in mind that a difference exists, 

 from the fact that the space between the concave and cylin- 

 der teeth is about three-sixteenths of an inch in the rice 

 machine instead of about an eighth of an inch, as it is in 

 the regular. When the rice is in good condition, the 

 amount hulled and broken should not exceed five per cent., 

 but when the grain is "sun-cracked", the percentage may 

 be somewhat larger. The condition of the grain will deter- 

 mine the number and position of the concave teeth, two, 

 four or six rows being used as required. 



Besides requiring a special spacing of the cylinder and 

 concave teeth, the cylinder speed must be lower for rice 



