136 SCIENCE OF SUCCESSFUL THRESHING. 



nals extending beyond 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 cylin- 

 der comes to rest at any point. Care should be taken not to 

 mar the journals in placing them on the ways. 



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 necessary, 

 until they are firmly seated. In driving them in, it is neces- 

 sary, however, to use some judgment, for as the concaves 

 are of cast iron, they are liable to split if the teeth are driven 

 in too hard. 



Setting the Concaves. The concaves should be adjusted 

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

 are usually required for wheat and barley, but for damp 

 grain six rows will be necessary. Rye can usually be 

 threshed with two rows, but the cylinder speed should be 



