154 SCIENCE OF SUCCESSFUL THRESHING 



the teeth are driven in and tightened with a long-handled 

 wrench and then driven in and tightened again, but they 

 are liable to get loose the first few days unless special at- 

 tention be paid them. If a tooth be allowed to remain 

 loose for any length of time, the hole will become so mis- 

 shapen that the tooth cannot be kept tight thereafter. The 

 teeth should be kept straight, not only so they will not 

 strike, but also so that they will pass at equal distances 

 from the concave teeth on both sides. 



Cylinder Speed. It is very important that the cylin- 

 der run at the proper speed. If run too fast, there is dan- 

 ger of cracking the grain, and if run too slowly, it will not 

 thresh clean. Then, too, the work of separation and clean- 

 ing is very much easier if the cylinder runs at the proper 

 speed and is never allowed to get below it. The motion 

 must be uniform if the best results be expected, for every 

 time it is allowed to get much below or above the correct 

 speed, the separator is liable to waste grain. With the 

 regular pulleys, the large 2O-bar cylinder of the Case sep- 

 arator should run at 750 revolutions per minute to give 

 the proper speed to the other parts of the machine. The 

 regular speed of the small or 12-bar cylinder is 1075 revo- 

 lutions per minute. In threshing tough rye or oats, the 

 cylinder is subjected to more work, and often runs too 

 slowly if attempt be made to maintain the normal speed, 

 therefore, the cylinder should run faster than usual, say, 

 800 for the 2O-bar and 1150 for the 12-bar, in order that 

 the other parts of the machine may run fully up to their 



