Lee, I take that as a sign of progress that you are dealing w/ door locks This pic should help, there's a small pin (missing here) that hold the cylinder in. It's presence is probably masked with some corrosion etc, IIRC the body of the lock was staked slightly to retain the pin but once installed in the housing it has no place to go. If you start drilling the pin with a small OD drill (smaller than the pin OD) it will probably just pull out, no damage to the pin's bore.
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