160 SCIENCE OF SUCCESSFUL THRESHING 



the boxes are marked as it runs. These marks show the 

 initiated at which end and at what point to drive the 

 weights used in the final balancing. A cylinder may be 

 balanced, though not as perfectly as is done at the factory, 

 by resting it on ways made by placing two carpenter's 

 squares on wooden horses. The squares should have 

 blocks nailed on each side to keep them on edge, and should 

 be carefully leveled both ways. Place the cylinder near 

 the center of the ways and roll it gently. Mark with a 

 piece of chalk the bar that is uppermost when it comes to 

 rest. Repeat, and if cylinder stops in the same position 

 three times in succession, drive a wedge under center band 

 at the chalk mark. Rub off the marks and repeat until 

 the cylinder comes to rest at any point. Care should be 

 taken not to mar the journals in placing them on the ways. 

 The cylinder may be out of balance by lack of the full 

 number of teeth. 



The Concaves. All that has been said about keeping 

 the cylinder teeth tight applies also to the concave teeth. 

 They should be driven in and tightened as often as neces- 

 sary, until they are firmly seated. In driving them in, it 

 is necessary, however, to use some judgment, as the con- 

 caves are of cast iron and are liable to split if the teeth are 

 driven in too hard. 



Setting the Concaves. The concaves should be ad- 

 justed to suit the kind and condition of grain. Four rows 

 of teeth are usually required for wheat and barley, but for 



