I make acceptable (not great) cracked rye, oats or wheat by setting my Lee
flour mill to the very coarsest setting. It would probably work on some
other mills as well.
But this is different from "steel-cut". The grain size is statistical, that
is, there are large cracked grains but some part of it is as fine as flour.
So I take the stuff from the grinder and put it through a sieve, keeping
the flour that comes out the bottom for other uses.
What's left in the sieve is pretty good cracked grain. Not perfect, because
many grains are bruised. But better than ordering a 50-pound bag of
anything. And it takes moments to make, from very cheap ingredients.
-Larry Geller