Ok for clarity then what tools are you using in the vids, they dont look like inserts, brazed tip? HSS
it is said that you can get a finer sharp edge on HSS so make cutting easier. too sharpe an edge on carbide makes them liable to chip the edge too easily especially on manual feed.
It also appears that the combination of surface speed, depth of cut and feed rate are what can make all the difference
saw a vid on this on here somewhere – fascinating 3" billet taking off 10,20,30 thou same speed same power feed only mid one gave a mirror finish
30 thou he upped the feed rate, and it came out fine? how do you work all this out
have not got a grip on this yet
perhaps cnc s/w does all this calc for you/