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

[irving2008]

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?

Thats correct... depends what size tool your lathe takes... could be as simple as grinding a flat on the bar, or a piece of square material drilled out 6mm with a locking screw. You can also get flat sided boring bars but not usually for that small a diameter hole although Chronos do one (second from bottom)

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?)?

I think Pete was refering to the hole diameter, but if you have a DRO then its easier, just dont rely on DRO for final diameter. Hole depth is as you say... assuming the centre hole in the chuck will clear the bar...

Found this video, its a start, there is a better one I have seen but can't find it right now