One of the most important requirements is disc blade concavity, that is, correct concavity. Further along we set forth the purposes of disc concavity. We feel it is important enough to devote the extra time and words in a discussion of the subject, because seldom is disc concavity talked about, and very few know that there is difference enough to cause good and bad work.
Small to mid-sized disc-harrows are a most useful tillage implement. Some farmers consider them indispensable. Discs such as the McD 10-A may be used with either tractors or big hitches of work horses. This tool will cut both plowed and unplowed ground. Ahead of the moldboard plow, the disc harrow is a valuable tool to cut up and free tough sod. When employed in tandem with spring tooth harrows, a great deal of work can be accomplished in much less time.