"Harold & Susan Vordos" wrote in message
. ..

... They're commonly referenced as spiral pointed taps. For blind
holes, a spiral fluted tap serves the same purpose, as it lifts the chips
from the hole instead of packing them in the flutes, which is the chief
cause of tap breakage when power tapping by using straight flute taps not
intended to be used under power.

Harold

Plus, you can do weird things like making worm wheels with them:

http://faxmentis.org/html/jpg/worm15.jpg

--
Jeff R.