TILLAGE MACHINERY 8l 



1 1 8. The spring-tooth harrow. This harrow is illus- 

 trated in Fig. 53. When the teeth are caught on any ob- 

 stacle they spring back and are released, this fact making 

 it a very useful implement for stony ground. It is also 

 an excellent pulverizer. 



119. The selection of a tooth harrow. It is a difficult 

 matter to give explicit directions for selecting a harrow. 

 The work to be done is the first thing to be considered, 

 as a smoothing harrow, for instance, performs a very 

 different office from a pulverizer or a weeder. Next the 

 workmanship used in its manufacture and construction 

 should be well examined. At all points where there will 

 be much wear it should be well reenforced, and should 

 have the general appearance of being a well-made tool. 

 The connection between the sections of the evener espe- 

 cially should be properly reenforced, as the work of a sin- 

 gle season has been known to wear out these connections. 

 The tooth fastener is another important part in a tooth 

 harrow which demands the attention of the purchaser. 

 The tooth should have a head so that it will not drop out 

 and be lost in case the fastener should become loosened. 

 The square tooth is desirable, though spike teeth are 

 made either from round or square stock. The regular 

 sizes are J/ inch and ^ inch, the ys inch size being suit- 

 able for heavier work. The number of teeth to the foot 

 of the harrow may vary from five to eight, and this num- 

 ber as w r ell as their size should correspond to the kind of 

 work and conditions under which the harrow is to be 

 used. Originally wooden harrow frames were the only 

 kind used, but now they are generally made of steel pipe, 

 angle and channel bars. The later styles of harrow are 

 much more durable, and, the same amount of material 

 being used, there is little choice between the styles of 

 steel harrows. Lever harrows have an advantage in that 



