@coppercone,
That's what happens if you use ordinary steel pins (or other fasteners) in aluminum. It only takes occasional condensing humidity for the interface to suffer from significant electrochemical corrosion, and the corrosion products of both aluminum and steel take up significantly more volume than the parent metal, so close fitting fasteners will seize in place. Aluminum + stainless steel is somewhat better as then only the aluminum corrodes, but if you want trouble-free reassembly in the future, if dissimilar metals are involved and one is a light alloy, you need to use an electrochemical corrosion inhibiting and passivating jointing compound, e.g.
Duralac@All,
I suspect the O.P's project is FUBARed and the hole tolerance is too coarse for any guaranteed press fit. If you play around a bit with the calculator ConKbot linked, the hole specs out at 1.985 H8 and there are *NO* H8 hole press fits in the associated tables.
You might be able to bodge it with a knurled pin and the right grade of Loctite!