THE CYLINDER, CONCAVES AND BEATER. 133 



to permit the moving of the cylinder in case the cylinder teeth 

 do not come exactly between the concave teeth. Do not 

 crowd cylinder box so hard against the cylinder head as to 

 cause danger of heating. It is best to leave about 1/64 of 

 an inch end play. 



Tracking of Teeth. All regular Case 20 bar cylinders 

 have five teeth which pass in the same space between the con- 

 cave teeth, during one revolution, "five teeth tracking" as it 

 is called. The 12 bar cylinders have three teeth tracking. 

 Some machines of other manufacture have two and some 

 four teeth tracking, and some have irregular spacing, as, for 

 example, three and six alternating. The effect of this latter 

 arrangement is to take twice as much straw through some 

 concave spaces as through others. 



Cracking Grain. The cut on the following page is full 

 size and shows the actual distance between tjie concave and 

 cylinder teeth of our regular cylinder. It is shown to em- 

 phasize the importance of having the cylinder properly ad- 

 justed endwise and of keeping the teeth straight. Supposing 

 all the teeth to be straight and that the cylinder be moved 

 1/16 of an inch to one end. Then instead of there being 1/8 

 of an inch space between the cylinder and concave teeth on 

 both sides, the cylinder teeth would be 3/16 of an inch from 

 the concave teeth on one side and only 1/16 of an inch from 

 them on the other. This condition of affairs would allow 

 the heads to slip through without being threshed on one side 

 of the teeth and on the other would crack the grain and cut 



