According to :

[ ... ]

The strongest? That may depend on the maker rather than the type. I
like Greenfield when the company is paying for them but my personal
stock is mostly cheapies or second-hand good ones that I have reground.

The most likely tap to get broken is a carbon steel tap in the
6-32 size. This is because the thread is too coarse for the diameter.
Note that the 32 TPI is commonly found in three sizes -- 10-32, 8-32,
and 6-32. 6-32 should never have become a standard.

HSS is stronger than carbon steel.

Two-flute is probably the strongest of the ones available in
6-32, and for anything other than blind holes a gun tap would be my
choice.

Other than these comments, I think that the OP's questions have
already been well answered.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---