Making rings without soldering ends together

Dear All,

I have a fabrication problem.I am trying to make mokume gane rings.
Of course, I do not want to make sheet and solder the ends together.
I tried the following with silver first, just to try, and I am not
pleased. I made a thick round ingot and rolled it out until it was
4.20 mm square. I sew a piece of it of 41 mm long, drew a line at
2.10 (the middle) and two other lines at 2 mm from each end. I
drilled 2 holes at each of the intersections of these lines using a
drill bit of 0.8 mm. I then connected the holes by sewing from one
end to the other. After annealing, I pried the bar open until it
fitted onto a mandrel. I annealed again and tried to make the hole
round, making the ring. The problem is that the ring ended up being
round at the inside, but not on the outside. At the two places where
the holes were drilled, the metal ‘caved in, 80’ creating a ‘V’ - it
looks likes someone started to saw there with a thick saw blade. The
’caving in’ is approximately 1 mm deep - too deep to file out
without making the ring too thin.

Could someone please explain what I did wrong? Should I leave more
than 2 mm from each end to drill the holes? Is a drill bit of 0.80
mm too thick?

Any help would be appreciated.
Have a good ‘dimanche’ and thank you,
Jacques Pinaud