I recently purchased 2 sets of the pre-ground HSS sets, in 1/4" and 5/16".
(catalog/stock# H5870 & 5871)
While some of the pre-ground sets may include an internal threading cutting
tool, these sets do not.

If anyone is temtped to buy these pre-ground sets, and expecting the
internal thread cutting tool, be certain that it's included before
purchasing.
The internal threading tool is shown and described as included in the H5687
& 5690 sets (costing almost $60 per set).

I don't anticipate that the HSS is a high grade (made in India) but some of
the low grade HSS blanks I've gotten from Enco hold up fairly well in any
operations I've used them for.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html