Could you perhaps have an end mill with catch-holes on the insides between the teeth(?), leading to a central hollow in the end mill, on which a vacuum is pulled to pull the material through and out, allowing the end mill to just bore continuously? (Sort of a very tiny solid-state version of a tunnel-boring machine, if you can picture that.)
That’s not feasible for a few reasons. The size difference between a cutting tool and the chip it produces is much smaller than the difference between a digging machine and rocks/gravel. The relative strength is also an issue, strings of steel or aluminum aren’t going to be sucked into a hole as readily as loose material. Lastly the geometry of a cutting head would be tricky if you need the chip to go towards the center instead of being thrown out. I guess it could work if you were milling something that turns into a fine material, like graphite. (Now THAT was a messy day in the shop)
Specifically re: strings, though, I’ve always wondered whether—as a separate problem—it’d be possible to have an end mill or drill that dices long stringy chip into shards. Seems like it’d make operation/maintenance easier in some respects. Maybe a bit with two parts, where the tip (either end mill or drill) has counter rotation against teeth running down the rest of the bit, such that the chip gets sheared as it encounters the interface between the two parts?
It does, but the ability to evacuate material straight out of a hole is very limited. Some are designed for side milling only, others can do plunge cuts but it's mainly done to expose a new "shelf" so that the bulk of the material removal can be done using the side of the tool.