In processing a crop for either human or animal consumption, it is generally necessary to reduce its size by either grinding or crushing it. This process is useful for correct feeding of livestock, since it increases the digestibility or palat-ability of the crop and also facilitates mixing it with other constituents of the feed. There are three basic kinds of mills used to crush or grind the harvest: (1) burr mills with either stone or steel burr plates, (2) roller mills, and (3) hammer mills. Before it is stored, the ground material is usually graded by sieving, as different sizes of material are used for feeding the various farm animals. For example, a coarser mixture is used for beef cattle, sheep, or laying hens, and a finely ground feed is more suited to high-producing dairy cows and young chickens. Oats, owing to the presence of fiber in the husk, are usually ground to a fine state for poultry feeding.
According to W. C. Krueger, author of an article entitled "Basic Principles Involved in the Design of the Small Feed Grinder," which appeared in the July 1927 issue of Agricultural Engineering, "the problem of feed reduction has always been of vital interest to farmers. From the time of the first horsepower burr mills to the largest present-day attrition mills, the progress in mill development has been towards faster, cheaper, and more economical grinding. Custom mills operated by waterpower or steam supplanted the use of the individual horse-operated mills. The development of the gas engine, however, resulted in a revival of the individual farm mill, improved and reduced in cost by this time."
Krueger goes on to explain that with the coming of electrical power to villages and country towns, custom feed-grinding enjoyed a brief revival. The new attrition mills produced a feed of better quality than that ground in farm mills, and fanners once again brought their feed crops into town for grinding. Later, when electricity was available to everyone, even rural dwellers, farmers began investing in electric motors to run their own mills.
Today, most milling is done right on the farm. The self-sufficient small farmer needs a mill which will serve a variety of functions involving both the household and farm. He should seek long-term economy and durability while satisfying his every milling need.
A burr mill is generally a better choke than a hammer or roller mill if you will need to do fine milling for household flour. Hammer mills are quite popular on the farm for grinding animal feed, but they do not produce a uniform grind, and are therefore not appropriate for milling flour. They are rugged and can grind different kinds of dry material at one time into different textures. Probably the most expensive mills to buy, yet the cheapest to operate, are the roller mills. They put out a good-quality feed, produce little waste, have a high-production capacity and require little power.
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