I have an "Archer" tapping head the small one that goes up to 1/4" or 6 mm. I used to have lots of 6BA 10 mm deep blind holes to tap in hard aluminium. Spiral flute taps would break very easily. I found that straight flute, carbon steel taps gave the best performance along with WD40 as a lubricant. It was because of breakage problems that I ended up with the manufacturers representative visiting me.

I no longer have the jigs that were used, but the technique used was to drill the hole to be tapped 20 mm deep, all sixteen of them on each disc edge. Do a pile of them and using the same jig, thread to a depth of ten mm using the depth stop on the drill press. This way the tapping chuck always reversed at the same point.