Need a perfect 8mm hole - to ream or bore?

[HankMcSpank]

Yes, you need one like this 5mm head on a 6mm shank (top one on page). If your normal lathe tool is bigger than 6mm then you might want to make up a boring bar holder (or buy one) to hold the cutting edge at the right height.

Ok, I'm seriously beginning to doubt my ability to visualize things here - that boring bar you linked to has a round shaft, but boring bars mount into the tool post? (which needs flat/square sided tools) - therefore there must be a boring bar holder with square edges in the equation?

Bill...thanks for the advice about making one, but I'm far too novice at this to think about making a boring bar at this stage (I don't even know how to use one let alone make one!)

Pete - re measuring the progress through the hole - well my mini lathe has DROs I figured it'd just be a matter of zeroing the DRO as the boring bar enters the hole and then taking it thru in until the DRO reads 35mm - that way I know I've cleared the hole? (or again am I missing something here?)

Thanks for your help thus far - I really wish someone had made a youtube video about boring out a whole. (it's no doubt a breeze once youve done it once, but never having even seen the tools I need, it's a little bit hard for me to visualize right now!)