44 



SCIENCE OF SUCCESSFUL THRESHING. 



be of the .right thickness to just fill the space, loosening the 

 set-screws and tightening the cap-screws will leave the shoes 

 free to run and with no lost motion. When the engine runs 

 "under," as in threshing, the wear is mostly on the upper 



FIG. 12. THE CROSS-HEAD. 



shoe and guide, and when engine runs "over," as on the road, 

 the wear is nearly all on the lower shoe and guide. Usually 

 the wear being nearly the same on both, they should be set 

 out equally. 



The Main Bearings are adjusted by removing paper 

 liners. Take out only a little at a time. If one of the bear- 

 ings heats and does not cool when the nuts are loosened, 

 remove the cap and clean out any grit or dirt that may be 

 found. If the babbitt be rough and torn up, it should be 

 scraped smooth. It is well to "relieve" the main bearings a 

 little at their edges, as explained for the connecting-rod 

 brasses. When the paper liners have all been removed, and 

 the shaft has lost motion, the boxes will require re-babbitt- 



