Fitting New Headset Bearings

Dr Nosh

Well, its really more to do with ‘How do I know I have the correct parts before I start the assembly process’?
I’m rebuilding a 1952 Claud Butler frame set up, with original forks, as a fixed.
The new headset bearing set is a NOS Tange Falcon
The fork crown measures 26.9mm dia
The old crown bearing measures 26.95mm dia
The ‘new’ Tange crown bearing measures 26.3mm dia.
Which is correct for current ‘modern’ parts replacement?
I could modify the fork crown or turn out the crown bearing.
However, something else to consider:
The fork crown shoulder is 3.6mm high.
The new Tange bearing has a 45 deg recess on the bottom side, giving a 1.7mm fitting face.
3.6 – 1.7 = 1.9mm engagement. Not enough in my books.
What is the current standard for engagement of bearing to crown?

What about stack height?
I have measured as follows:
Crown bearing 8.5
Bottom cup bearing 16.4
Frame head tube 142.3
Top cup bearing 13.2
Total 180.4
The fork steerer tube measures 174 crown top face to top of tube.

So, you can see the conundrum.
If I then source an alternative headset bearing set, how do I specify what I actually need? :? :?

Tail end Charlie

Take your bike to a good LBS and let them have a look. Sorry can't offer anything else.