At the object level . Permissions allowed or denied at the object level apply to the entire object. For example, you can set an object-level permission on an OU object that allows a particular group, such as Account Operators, to create child objects in the OU. At the property level .
Ball mills are used in chemistry and in industry to grind hard solids to a very fine powder. They are very similar to rock tumblers. Basically, the idea is to rotate a container filled with heavy metal balls that crush the substance that you want to grind.
Uses. 1  Grind your own bird feed (obviously don't use lead balls for this). 2  Grind sand for glass making. 3  Grind metals like aluminum and magnesium.  Grind your own green sand for use in metal 1  casting. Grind a mixture of chemicals so that they will react faster when you put them in a furnace or otherwise heat them.