Hi Max! As always - great professional research there. I totally agree that a blade intended for manicure in a horticultural context would require a specific grind angle that produced lift.
Some-times I am such an idiot in how I say things.
I did mean to mean that 'neutral lift' related to the sickle bar context. The speeds were way slower than rotational forces on rotating blades.
I also meant that in using slasher mowers to cut high grasses the lift may be much less significant - maybe irrelevant.
However, you have made me think this through: -
The history of sickle usage for grass cutting throws up an anomaly - Sickles and scythes were used early morning and late afternoon when the grass [now cooler] would stand-up and be presented to the blade. History tells us that the reel mower overcame this trait, to the relief of country folk that complained about the noise created at these un-godly hours.
I do feel you must be right here: Any blade that can be sharpened on one side will produce lift at high rotational speeds.
The early rotary - the Rotoscythe - had circular blades ground towards the middle [a 'V'] that enabled the blades to be reversed - as in your patent.
For manicure in a horticultural context, blade design must be crucial. I did want to distinguish between flat blades and fluted blades in my original posting above. You have shown this must be a matter of degree, and not the nonsense of 'zero lift' I spoke about in relation to mowers intended to turn grass into lawn.
I have been reminded about the physics of tip speed with the Bloodhound Project.
