Jason -- most of those from small drills are threaded for 3/8 by 24, and some have a place for a locking screw that threads into the fitting.
If you look on the body (often near the bottom or on the bottom, most have markings for what the mating threads or taper is. JT3 and JT33 are common, and the adapting arbors are readily available from a number of sources (Enco, Little Machine Shop, JohnnyCNC and others).
My little metal lathe has a 3/4 by 16 thread and I have a number of drill chucks threaded for that.
I have been looking for a MT2 to 3/4 by 16 in case you see a source for those (not common).