l62 SCIENCE OF SUCCESSFUL THRESHING. 



certain slow speed as already stated^ and when so speeded, 

 more concave teeth are required than if it were allowed to 

 run faster However, since the cylinder speed must be low, 

 a sufficient number of concave teeth should be used to 

 knock the peas out of the pods. For "blanks", when less 

 than six rows of concave teeth are used, hardwood boards 

 cut to the right length and width and fitted to the concave- 

 circles are preferable to the regular iron-blanks. Since peas 

 are apt to be cracked by the corners on the iron-blank-con- 

 caves or grates, the 'grates under the beater are sometimes 

 covered with sheet-iron. This should be done where trouble 

 from cracking is experienced. 



In general, the adjustable chaffer and shoe sieve should 

 be set only slightly more open for the common field peas or 

 for stock-peas than for wheat. If the separator be fitted 

 with common-sieves, the one and one-quarter-inch lip, E, 

 or the two-inch lip, D, should be used as a chaffer, and the 

 three-eighths-inch lip, G, should be placed in the second 

 notch and third hole in the shoe. For a screen, the three- 

 sixteenths by three-quarter-inch oblong hole, P, is best, 

 although the fifteen-sixty-fourths round-hole wheat sieve, 

 H, works very well in field or "Whip-poor-will" stock- 

 peas. 



If trouble be experienced because the peas strike the 

 floor of the shoe and bound over into the fan, it can be 

 prevented by covering the front part of the chaffer to a dis- 

 tance of twelve or fourteen inches with sheet-iron. If there 



