Help - Headset won't fit!

Rebuilding 1990 ish Colnago with new Record headset. Upper and lower head tube cups ( races ) will not fit. They measure ( with mic )30.27mm, the head tube ID is 29.9 mm ( measured with vernier calipers so might be 30.0 max. ). According to Sheldon Brown dimension should be 30.2 nominal. I would expect approx 0.1 for interference fit so that would make sense with new headset. Head tube therefore seems undersized. Any classic rebuilders had this problem and what did you do?
PS. I have fitted headsets before and have the tools albeit homemade.

Have you tried putting the cups in the freezer so that they shink slightly, and the frame next to a radiator so that it expands? Might work.

Otherwise an engineering place could turn down the cups by 0.1.

It's the difference between JIS and ISO. There may be a problem with the fork crown race too. You can be brutal and keep winding the press, but the lugs might split. If the crown race won't go, 26.4 to a 30mm crown, take it all to a shop and get them to ream to size.

Bigger hammer murts?

Hi, I doubt that Colnago or Campagnolo have ever had much to do with JIS! Crown race fitted fine. Before I turn to my lathe I just wanted to be sure I was not missing a trick. Heating/freezing might help but I sense something more fundamental is wrong here. The original headset was obviously fitted by a gorilla and shows evidence of his bute strength.

Trudat.

Get the headtube reamed and faced?

^ That.
Needs re-reaming.

Bigger hammer murts?

that