I have an old front door with a lockset that I can't for the life of me
get out.

It's an old Schlage - could date back 15 years or even more. It has the
key-in-knob lock.

The inside knob came off easily enough. But the outside knob will not
come off.

There's some sort of interlock between the latch (the part that engages
the door frame) and the square shaft that joins the knobs.

There's no apparent release mechanism, no visible screws, pins, etc.
holding it together.

The latch part will come out about 1/8" before it stops.

The outside knob will come out about 3/16" before it stops.

And the guts that the inside knob was attached to come out about 3/16"
before they stop.

After that it all seems to hit some kind of pin/interlock and nothing
will come out any further.

I could drill it out, but that would create a huge mess of filings. I'd
rather find a way to get it out sanely....

--Yan