Those videos are actually quite good at illustrating the basic concepts behind tool geometry, especially the part that discusses shear planes and how varying rake alters the length of the shear line.
I also liked that they had a Kw meter to show how increasing amounts of side rake reduces motor load. In effect, what this means is that increases in side rake reduces cutting forces. While it will reduce the load on any lathe, another way to look at it is that increases in side rake will enable a lighter lathe to make cuts that it otherwise may not be able to make.
I've never seen a presentation that showed how back rake, when combined with side rake, channels the direction of chip flow. I know this occurs but this is the first time I've seen it in a video - very cool. All to often when we discuss tool geometry here we say in words what this video series shows much more clearly. Thanks for bringing this to our attention, Jon.
Now of course, you have to be able to apply these concepts to the actual grinding of a turning tool.
