One thing I have done in the past when needing to do something such as that and no tooling is available, is take a small HSS or carbide endmill that you really don't care too much about.....2 flutes is the quickest and easiest to make this out of.
Grind away all but one flute and mount it in your toolpost and use it the same as you would a boring bar that you don't have......
Best Regards,
Russ
Grind away all but one flute and mount it in your toolpost and use it the same as you would a boring bar that you don't have......
Best Regards,
Russ