Best way to adjust a boring bar bit is to clamp a depth mike to the bed,
over blocks, with the mike spindle centered at same hgt as the bar and
square to the lathe axis. The overall position of this rig is close to
the work. Tye bit is then bought into position and the mike set to
refer to the tip position. Then yu loosen the clamp screw for the bit
and dial off your new setting. It's wise to check that after clamping
the bit again. The mike gives you a means of making very small
adjustments to the bit position relative to the bar axis. If you're too
ham-fisted to get it exactly right, you can set out a bit more and them
stone the bit edge back to spec.

I use this trick often enough when boring in my hor mill, for which I
have no indexing boring bar holder. I have never had any trouble hitting
..0005" on dia, or less.


Regards, Hoyt McKagen

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