Why do you care so much about how thick the chip is?
Feed per rev/flute, not chip thickness, is going to determine scallop height and resulting surface roughness.
Same feed rate with .005" finish pass or with .02" finish pass should produce similar finishes. Chip thickness will be much different. Why bother with chip thickness nonsense?
Two things, let's consider a 0.005 finish pass:
- Seeing what the actual thickness would be at any given feed/speed combination. Knowing that, I could apply a specific final thickness to a variety of tools/sizes/speeds and adjusting the feed to match a known good value.
- Getting insight into cutting pressure and deflection. A thicker chip could mean I would need a spring pass because of cutter deflection. Or I could find optimal chip thicknesses for certain diameters that give me the results I want.
Sure, I could look at overall FPT and just use that. But I still don't know what the actual chip thickness really is. Do I need to know? Not really. Would I benefit from the extra information? IMO yes.