Tight (not) fitting crankshaft seal in timing cover

I am on my second new crank oil seal in the timing cover. The first disintegrated after forcing with a socket used as a drive. The original seal had practically fused in place and had to be scraped out bit by bit. Now the hole appears 1mm too small.A new seal is a tight fit at the top of the hole but impossible beneath the circlip, where the hole steps in, making seating the seal impossible.Am I doing the right thing having the hole enlarged and is there a size for this? Both the Andover Norton and Wassel seals supplied look to be an inch external diameter.I am new to the NOC and almost new to mechanics but my Interpol project has already thrown up a crankshaft without a rotor key on the DS.. awaiting a fix so I am not feeling confident.Thanks in advance, Mike