Now a scan to show that even fine gaps are not really a problem.
I have scanned a needle:
Unfortunately, I forgot to take a photo on the scan helper 
Fusion settings : 0.08 Advanced
Meshing settings : 6
on the second picture I noticed that the needle looks crooked - so I took a closer look at the needle:
… and it is crooked
now to the dimensions:
I am very satisfied with the result