In my imagination (fwiw), they would be drilling and cutting from top down. from under, they would have all the hydrogen gas trapped at the top in a bubble, and it would be impractical to work there due to (if nothing else) to sparks emanating from the commutator on the drill motor as it rotated past the brushes.
Although, one thing that *might* work is a running water spray (from above and working from above) which would act to prohibit sparks from occurring on the bit surfaces, eg, steel-on-concrete and steel-on-steel. (But one would have to have balls of titanium...)