Tube OD vs "O" dimension on Crown

[PostwarO27]

I have a case with a tube dimension of 2.0mm.  I know my "O" dimension on the crown should be at least that.  I also know as a toolmaker that fitting a pin/bushing into a bore that is the same size is a press/friction fit.  My question is does an "O" dimension on the crown have the clearance needed to turn.  IOW if get a crown with an "O" dim of 2.0 will the actual dimension be, for arguments sake, 2.2 or will it actually be 2.0?

 

Thanks in advance.

[praezis]

14 hours ago, PostwarO27 said:

... "O" dim of 2.0 will the actual dimension be, for arguments sake, 2.2 or will it actually be 2.0?

Rather 1.8 - else there will be no sealing.
But a crown for 2.0 tube will have the right gasket.

Frank