7O FARM MACHINERY 



furrow. One inch width of bearing surface for 12- and 14- 

 inch plows and ij^ inches for i6-inch plows is the average 

 width of this bearing, more being needed for soft, mellow 

 soils than for firm soils. This fact necessitates a change 

 in the plow in changing from hard to mellow soils, as a 

 share set for a hard soil will swing to one side or work 

 poorly in the mellow soil. A handy device called a heel 

 plate is sometimes used to vary the width of surface at 

 the heel. 



104. The set of sulky plows. With the sulky plow, 

 when the share lies on a flat surface, the distance from 

 the heel of the landside to the surface is called the suction. 



FIG. 49 THE BEARING SURFACE REQUIRED AT THE WING OF THE SHARE 



In sulky and gang plows this is usually ^ inch. The 

 entire downward pressure or suction should be carried 

 upon the wheels or carnage, which, with their well lubri- 

 cated bearings, will reduce the draft and require no bear- 

 ing surface at the wing of the share. In order to reduce 

 the friction by removing the pressure from the landside, 

 the rear furrow wheel is set outside the line of the land- 

 side, usually about i% inches. 



105. Set of coulter. The rolling coulter should be set 

 to clear the shin of the plow by about J4 inch, and should 

 cut l / 2 inch or VA inch outside the shin. It is said that if 



