Without knowing exactly what bearing you have it's hard to give an exact answer. Generally speaking, you do not want a very tight fit at all. I'm assuming a taper bearing of around 1-2 inches or so. Maybe 0.0002 to 0.0004". Anything tighter than that and you risk damaging it or warping it out of shape.
Whenever I need to bore a hole to fit a bearing I contact the bearing manufacturer by email and ask them for clearances. There are so many different bearings and the fit has a direct impact on internal bearing clearances. The maker will know what you need. Being able to bore to that dimension, which will usually be in the micron range ... is another thing.
in an automotive application i sometimes need to spray weld the spindle (and turn to size) and sleeve/bore the knuckle (part the cup rides in). the spindle to bearing is .002 press (2" spindle), the cup is "0" fit
If using tapered roller bearings you can utilize a fair amount of press fit as the bearing clearance is made up between the bearings, ball bearings the clearances are built in and cannot stand much press. Tapered rollers don't like out of round.
One more thing, with aluminum housings we put a tad more press on the bearings compared to steel as the aluminum can heat faster and expand faster and sometimes the brg can start spinning. Nice thing about tapered brgs they can stand the press and not self destruct.