Reply by live4ever

I believe it is the fact that most spiral bits are made of solid carbide that makes them fragile, not necessarily the upcut/downcut/spiral design.

FWIW, you can get spiral bits in HSS that don’t have the fragility issues of the solid carbide bits. Of course, they won’t stay sharp as long as the carbide ones.

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.