Hi Brian,
To avoid rubbing, the tools will satisfactorily only bore holes with diameter at least twice the tool-size, without modification. So, a 6mm tool will only bore 12mm or larger holes and so on. This is because the business-end looks very much like 1/4 circle. You can relieve them slightly but basically that's the limit.
I set mine to cut on-centre but can see that a gnats above also makes sense. I grind mine pretty much as they came so that they cut like a left hand knife tool as they are plunged into a hole – taking account of the necessary clearances inside the bore.
I'll take a photo when I get chance.
My other boring tools follow the sort of design described here using 7/16" or 1/2" MS…
**LINK**
The one described here is for refining a bore with shear-cutting.
Jon