Our grain mill was often called an “elevator.” It had a large silo for storage. It was not like ancient mills using the grist mill type milling. Instead it was called a “ball mill,” Or a “hammer mill” (no grist wheels anymore). Ball mills use a large number of steel balls in a rotating cage crushing the grain against a screen, thru which the proper size grist is screened. Or if hammer mills, then lots of small rotating hammers do the same. They also had a “rolling mill” to roll grain (squash it — like quaker oats) so that cattle can more easily digest them. Rolled oats were favorite horse food — like candy to them or cattle.
How often you go is exactly like you buy groceries. as often as you need for your particular requirments/blended, of course, with economics of size. Like any food item, milled grain is candy to vermin, so you really do not want to attract them, nor see milled grain be ruined by moisture, etc.
If you took a pickup load of wheat (or whatever) to the mill. You would dump it into this hole in the floor covered with a metal mesh or grid — the grain then went via chain elevator up to the actual milling devise, ground, and then dropped down into the same pickup bed via a chute. Or they would put it into a sack for you. The mill building sat astride a spur of the railroad, so it could easily load stored grain directly into rail hopper cars. All dairy farmers used various milled grain — usually a mix per their specs — specially blended for them. In fact the proper mix, completely mixed, was half the value of using the mill. It was hard to do the proper mixing by hand. Cows, hogs and chickens must supplement hay or grass with grain in order to produce the amount that we have become accustomed to. My dad got his particular mix of wheat, barley and oats by planting that same mix. when combined, then it was already mixed in proportions he liked.
During and after WWII, entreprenuers fashioned portable hammer mills on a small truck bed and went around to farmers to do their milling on site. After 1948, dad managed to buy a small hammer mill, which we installed permanently in our barn.
Clear back in 20s and 30s entrepreneurs also used to go around with big circular saws mounted on back of a truck, to use to saw firewood on site. They were very dangerous, most folks thought that they were so practical in everything, that no way could they get hurt. Wasn’t a very workable, or for that matter practical, attitude! They had no safety equipment whatsoever.
Those same 2′-3′ circular saw blades often cracked and then couldn’t be used. We traded for the broken parts and made all our butcher knives from them. We never bought knives!
Model T’s were famous for being put to work to do the most innovative tasks imaginable.