Norton 16h Dollhead Gearbox

Loosen the split clamp to take off the lever and then push the shaft inwards.

I think your trying to release the outer cap from the brass body to get the felt  replaced.  Brass body steel cap  can be a little difficult to part. The oil cooking into the threads and  seizing.  I would  try a night in the freezer , then grip the thread in soft jaws and apply some gentle heat to the cap.  The nut is 3/4” Whitworth, or 33mm if you don’t have one.  Once it frees it usually spins off.  
 

Be careful with the old felt, oil soaked inside too much heat and it could set alight.  A couple of cycles like this should work eventually without damage to the brass.  As David says the worm should wind out easily enough once you release the lever.

Jon.  

… it may be worth putting it back into the casing after a few heat cycles and tightening the cap. It may just crack the grip then undo it as normal….  Don’t go nuts and damage the casing… 

it’s an old trick a cabinet maker shared with me for rusted in wood screws.

Cheers

Jon

Forget the felt oil seal as it is laughingly called. I fitted a 1/2 inch bore double lipped oil seal which fits perfectly in the chromed cover. You can fit first with a dab of oil on the shaft, clean the inside of the cover nut add a little epoxy resin to the face of the seal or inside the cover and screw into place. No more weeping or drips.

 1/2

Worth a try; as you say the felt only soaks up the oil to deposit it over a longer period.

Cheers

Jon