I follow Stan : chaindrilling will be a lot faster than first going
shopping for a tool of any sort. I understand it is one hole only? Its
fast only if you mark your holes exactly on a circle and mark each hole
on that circle with dividers same radius as drill. Start with a small
drill like 4.5mm and finish 6mm. Tedious marking, but little filing i.e.
nicer work doing it precisely.
Any home- use type hole saw would loose half its worth with this Job,
usually they are built for very low RPM and burn out the hand drill
and/or get blunt half way through.
-protect your eyes-

ede wolf