"Normal tooling should be mounted on or just a hair below centre" Well
aeronut...all of those years ago...in Australia our Trade Technical Apprenticeship Instructors were more specific at ~~~~ 0.003" below DC when using HSS parting tools
However at work I was fortunate in being under the watch of an older English Toolmaker ...his specific recommendation...
"was place the tip of the tool just below DC by about the thickness of a roll your own cigarette paper" I did measure the cigarette paper & the best average was between 0.002 & 0.003"
This chap also suggested that HSS parting tools with a flat tapered top rake were rubbish, as the tapered top rake must also include a chip curling radius....[with the radius being about 10 times the thickness of the parting tool]
Still works......one issue not covered here is the cutting fluid specific to the material being machined....
In todays world, tooling manufacturers recommendations for CNC applications [computer assigned speeds, feeds, material grade, coolant flow etc] is text book reference reading only and should not necessarily be confused for a home workshop Myford or SAIG model lathe work
In the end is a Vauxhall better than a Volkswagon?
Derek