So far, my experience with spiral flute taps hasn't been great; they just seem to be too fragile, even in aluminum. Obviously, very desirable for getting the chips up and out the top of a blind hole. Have a job coming up (CNC with rigid tapping) that is 10-32 with 1-inch deep thread in a blind hole (Lots of them, in Aluminum). Most of my bad experiences breaking these are power tapping in a Bridgeport, but... Have never had any problems 30+ years with 2-flute spiral point, but tired of digging chips out of the hole. Worried about using spiral flute on this job.