george: Actually my new Dunhill 488 could use that tweak - care to elaborate on the process? That's one fix that I have not attempted.
It's straightforward. All that's required is a full sheet of 800 grit sandpaper; a wide strip of tape; a smooth, flat surface; and practice.
Tape the paper to the flat surface only along the top. All cutting/sanding will be PULLING, not pushing or side-to-side, and the paper must not be allowed to "ride up" in a bulge in front of the pressure. Taping only the top edge will prevent that.
Hold the stummel by its shank close to its end, like a pencil or pen when writing except straight up. Stabilize everything by letting the side of your hand touch the flat surface normally, and let it stay in contact when dragging/pulling the shank-end across the paper.
BE ABSOLUTELY POSITIVE BEFORE STARTING EVERY STROKE that the shank face is in flat contact. You must learn to feel it. It's a sensation similar to balancing something on your finger tip. With experience, it's almost a "suction cup" sensation.
When ready, apply a gentle downward pressure and draw/pull the stummel toward the elbow of your holding arm.
IF IT CHATTERS, STOP IMMEDIATELY and rotate the stummel an eighth turn or so and try again. Repeat as necessary until no chattering occurs. You want it to glide. Every stummel has a chatter-less "glide" orientation. You must find it before proceeding.
After a few 4"-5" drags, insert the stem into the stummel and check using a backlight. Locate the high spot, and repeat the sandpapeer dragging process while---and this is the tricky part---applying a bit more pressure to the high spot while still keeping the shank face in full contact with the flat surface. Sounds slightly crazy, like a contradiction in terms, but it isn't. It just takes practice and developing a "feel".
After a few "uneven pressure" drags, test the light gap again.
Repeat as necessary until all light gaps are gone.
Then re-stain the end of the shank with a NEARLY DRY Q-tip (so the grain isn't raised), and she's cooked. :D