Gummy metals cut better when marked with Sharpie or glue

[FEM2008]

Looking the videos, the action of the chip flow with the colored bands reminds me of laminar vs turbulent flow over a wing. It is important to keep in mind here that the effect they observed works with very small depth of cuts (a few thousands). I can see that adding some material on top with different strain behavior-such as glue-changes how the chip "micro" bends and have an effect, but with other applied materials, such as alcohol, there must be a different mechanism that's working. Meanwhile, adding a layer of Dykem or even superglue before a finishing cut is easy enough to do and try.

Another interesting finding from the paper is that alcohol seems to work for some aluminum alloys, but it does not work on other metals. Stephan Gotteswinter did a video not too long ago were he used alcohol as a cutting fluid for some CNC machining on aluminum ("More CNC Router Adventures" from a couple of months ago"). The initial study was published 2 years ago with a recent update that I posted here, so it is plausible that some have implemented this already.