Grains are drier and only have a little oil in their germ. You can grind grains in any mill, grinder or whatnot. Grains include wheat, corn, rice, oat groats, barley, rye, etc.
Legumes and seeds are a different matter. Peas and most beans are not "greasy", that is, you can not extract oil from them very easily. However, soy beans ARE "greasy", meaning that if you try to mill or grind them in a regular mill or grinder, you will soon have a coating of oil on the grinding parts. Think Soy oil - oh, and peanut butter. Some seeds are also "greasy" - think sunflower, flax and sesame seeds. Sometimes you can get away with milling "greasy" - IF you only grind small amounts at a time and IF you grind at a coarse setting and IF you then run some hard red wheat right after milling to clean the mill head, blades or stones. NO! Strike that! Do NOT try to mill peanuts, soy or sesame seeds with stones! It will KILL the stones. And it's not too good for anything else, either. Use a blender or food processor with a strong motor!
I have about 5 different ways to grind grains, most beans and some seeds to a flour.
1.) I have a wheat grinder. I bought if off of a guy that was moving and didn't want it. Paid $50 for a K-Tec mill. Such a deal! And after I talked about what I was going to grind with it and how to use it, he only half-jokingly wanted it back. No dice! This mill will grind all non-oily seeds, nuts, beans and grains. (Don't want to go making Peanut butter in the grain mill, it would kill it.)
When you mill, the grains/legumes/seeds must be CLEAN and FREE of debris or it will burn out your mill. Even LITTLE, TINY-TINY pieces of dirt/rocks will damage an impact mill. This is also a noisy machine and I mill OUTSIDE with it so I don't get flour dust in my house. It's a lot easier to just sweep off the porch than wipe up flour, mop the floor and clean off the wall like needs to be done when I mill in the house. This mill makes a very find flour - even on the coarsest setting, it's a pretty fine flour. And you can NOT make cracked wheat with this.
There are mills out there that don't make a mess. I just have one that DOES, but for $50, I'll just mill outside. My friend has a mill that is quiet and self-contained. It has one piece that the grain goes into and another piece that the milled flour goes into. The pieces are connected by an enclosed tube "shoot". Both of the pieces have tight-fitting lids on them, so there is no dust - EVER. Of course, she paid about $350 for hers. I'm too poor to afford that. lol And she can't make cracked wheat with hers either.
2a.) I have a "Back to Basics" mill. I bought it recently and I paid $50 for it. It turns easily. I can grind 2 cups of wheat in it in 1-2 minutes. It's not quite as fine a grind as my electric mill, but it works in a pinch or if you can't afford an electric mill. I use it to make a corn meal from popcorn that is a little more coarsely ground than my K-Tec makes - which is what I want for corn meal. I like it and wish I had bought it years ago instead of 2b. I can mill grains, seeds and legumes in it and I can also make cracked wheat with it.
2b.) I have 2 different hand mills. One is a "Little Ark". Paid WAY too much (about $175.00 nine or so years ago) for a very poor preforming mill. It does have both a set of stone grinding wheels and a set of metal burrs. Problem is, you either have to be a gorilla, have access to a gorilla or buy the parts and motorize it. And in case of power outage, you'd use it how??? It was supposed to be an "easy turning" model and it is NOT! I don't think it grinds all that well either. When I tried to get the pattern that was supposed to be included (so that the flour didn't go all over the place instead of into a bowl or pan), the company appeared to be out of business. I tried for years to get a contact for them to no avail. I can grind non-greasy grains, seeds and legumes in it, but it is VERY DIFFICULT to turn the handle. I can crack wheat in it, but again, it's VERY hard to do.
3.) Food processors will grind grains, legumes, seeds and nuts. It takes a lot longer to do with a food processor than in any of the mills. You don't want to try and grind too much at one time, but it has to be "enough" to grind. Usually about 1/3 to just under 1/2 of your processor bowl full is about right. It won't be as fine a grind as if it were in a mill. You can use a sifter to sift out the larger particles and regrind them, but it is time consuming. I used this method when I didn't have a mill. You can make cracked wheat as well as flour with this method. CAUTION: You can burn your motor out if you don't pay attention to what you're doing and let the motor rest when it starts to smell "hot"!
4.) Blenders will also grind grains on a high speed. My blender needs to have a 1 pint regular mouth mason jar attached to it instead of the regular blender jar. Most blenders will thread a 1 pint mason jar on their attachment ring so that you can use it to make smaller portions or to grind with it. Depending on the power of your blender, you can even make peanut and nut butters, but it takes a stronger motor or adding some oil to do it. Only fill the jar 1/2 full of grains/legumes to grind and know that it won't be as fine a grind as in a mill. You can use a sifter to sift out the larger particles and regrind them, but it is time consuming. I also used this method when I didn't have a mill. You can make cracked wheat as well as flour with this method. CAUTION: You can burn your motor out if you don't pay attention to what you're doing and let the motor rest when it starts to smell "hot"!
You can grind oatmeal in a blender very easily. Oatmeal has already been either flattened (rolled) or chopped (steel-cut) into smaller pieces, so the blender can handle it more easily. When my kids had chicken pox, I bought a package of that expensive stuff to put into the bath water. Then I read the ingredients and looked at what I was pouring into the water. I paid SIX BUCKS for 4 packets of ground oatmeal. That's what's IN those little packets. I know this, because I went in and ground my regular old oatmeal and it looked JUST LIKE the stuff from the packets! It WORKED just like the stuff in the packets. And with 3 little ones with Chicken pox, I went through the 4 packets in a couple of hours. Needless to say, I didn't buy any more of the packets! At the time, oatmeal was about $1.50 for the LARGE container that was a couple of pounds of oatmeal. Worth my 30 seconds of grinding to grind my own.
5.) Wallyworld has coffee grinders for about $10. They won't stand up to heavy duty usage, but you can grind spices and non-greasy legumes and seeds in them. You can also grind small amounts of wheat, but I think you'd probably burn out your motor if you tried to grind enough to make bread with it. It will grind beans enough for a couple of tablespoons to make bean flour with it, but I wouldn't try mill a cup or so of beans to a flour at one time. CAUTION: You can burn your motor out if you don't pay attention to what you're doing and let the motor rest when it starts to smell "hot"!
There is one other option for using wheat without a mill.
*Non-instant is a finer grind than "Instant". Non-instant is not found in most grocery stores. You have to get it from Food Storage places or in Utah at a regular store. Most grocery stores carry "Instant non-fat dry milk" in either store brands or name brands. Since the "non-instant" is a smaller powder than the "instant" it takes less of it to cook with. To use instant as "non-instant", either make the change in amount OR grind it in your blender or food processor until it's a powder instead of small "pebbles".