I too recently encountered this issue with a new frame from Italy. The measurement of the upper and lower headset cups measured about .28 or .29 mm larger than the internal dimension of the head tube. I solved the problem and completed the installation by doing the following:

First I took a 1 inch paddle sander which is made for use with a drill and is made of many separate sheets of paper bound on a 1/4 chuck and reamed the inside of the head tube. It works like a hone but does not need lubrication in the process. Apparently some internal burrs along with the chrome on top of that had reduced the ID significantly. The irregularities came off pretty easily and I gained back about .18 mm from that alone.

Next I took a standing belt sander to the upper and lower cup body not only to take a bit off but to create a more taper to get it started. This got me about another .08 mm on the insert portion of the cup body with a little more on the insert end. This is a pretty delicate job and should be done cautiously.

Then I put the upper and lower cups in the freezer and that reduced the OD of the cup body insert end by an additional .03 mm.

I got all of my parts and tools ready and greased, and then pulled the cups out of the freezer and got them pressed in while they were still cold. The pressure required was not excessive and the cup bodies went in nicely.

My only complaint is that in prepping the cup body on the belt sander I did mar the finished surface just a little in a visible area. Probably something that only I would notice but there it is! It wasn't that daunting of a challenge but I have never been one to shy away from taking power tools to new equipment.

The headset was a new Campy Record unit and the frame was custom made for me recently. If I had purchased the bike completely built they would have solved this in the shop and I would never have known about it. It probably happens more often than we think!

Good luck!

Yes, my racing days are over as well. Very fun times. Two strokes are intoxicating.

Thank you to everyone who replied with helpful comments.

I believe now that my frame just needs “frame prep” for headset and BB by a shop with proper toola and experience. The shop I use is qualified to do this. From what you all have said, it seems within tolerance for hand reaming. This is what I wanted to know.

My two previous frames I had headset and BB installed by the bike shop where i bought them. So I kind of freaked out trying to fit the crown race cup.

Stay safe out there,
Robin

Glad it's working out, sounds like a sweet bike.

That is good. I see you are in South Carolina, what shop did you use? I tend to use Charleston Bike company for all my Italian problems!

yes, Jeff at CHS bike on Savannah Hwy!

it is!
https://cimg9.ibsrv.net/gimg/bikefor...90a73c7f0.jpeg

You are in good hands. They will do it and they will do it right. Not many shops have solid "professional" mechanics. They do.