IO2 . SCIENCE OF SUCCESSFUL THRESHING. 



gear turns upon the shaft, when the differential-gear works, 

 and accordingly, it should be oiled occasionally through the 



hole provided for this purpose in its hub. The bevel-pinions 



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 also revolve about their shafts. An oil-hole is drilled through 



the center of each of these shafts, to provide for oiling them, 

 as is shown in Fig. 32. The hub of the left traction wheel 

 turns upon the axle in turning corners, and therefore should 

 be oiled occasionally. This is done by removing the cap- 

 screws in the hub of the traction wheel. 



