We do 16mm dia, over full depth, countersinks in 6mm thick mild steel plate by the hundred at a time. The core holes are 10.2mm.
Just wondered if anyone has tried the indexable ones shown in the J&L flyer, and if they are any good.
We've tried single flute, multi flute, all sorts, with varying longevity and results, yet to try a 16mm drill specially ground, or a spotting bit. Bob