86 FARM MACHINERY 



gangs often may be set to throw in or out from the center, 

 to suit the nature of the work. 



Usually the first parts of the disk harrow to wear out 

 are the bearings. There are many styles of ball and 

 chilled iron bearings in the market now, but those of hard 

 wood seem to be as satisfactory as any, since they may 

 be easily replaced. The construction of the bearings 

 should be such as to exclude all dirt. A reliable means of 

 oiling should be provided, and it is well to have an oil 

 pipe to the bearings which extends above the weight pans 

 or frame. 



The scrapers or cleaners to keep the disks clean are 

 another important feature of the disk harrow. These 

 may be made stationary or so arranged as to be operated 

 by the feet of the driver or otherwise when needed. 

 They are not needed when working in dry soil, and when 

 stationary they cause undue friction. A scraper that is 

 made to oscillate by horse power over the face of the 

 disk blades, and clean them automatically once in six 

 revolutions, is sometimes used. When not needed it may 

 be thrown out of gear. 



Disk harrows with bumpers to carry the end thrust of 

 the sections are usually made with one lever in order 

 that the gangs or sections may be adjusted and the bump- 

 ers kept squarely together. A scheme to surmount this 

 difficulty is to adjust the outer end of the gangs only. A 

 two-lever disk harrow offers several advantages by ad- 

 justing the gangs at different angles for side hill work 

 and for double disking by lapping one-half each time. 

 The soil when disked once is not as firm as the undisked 

 ground, and if lapping one-half, it may be necessary to 

 set the gangs at different angles in order to cause the 

 harrow to follow the team well. 



Jt is advisable to have good clearance between stand- 



