I finally attached the thread cutting kit to a sherline lathe. The kit
came with a 60 degree carbide cutter.

Even with 1/4" brass rods, that broke in probably minutes, followed by the
spare I had.

the cuts looked like **** too. They weren't really shiny and the "feel"
from the handcrank on the headstock/gear train didn't seem right. I was
only cutting 2 to 3 mils per pass.

I decided to gring my own with 1/4" HSS steel blanks on a Tormek knife
sharpener.

That worked much much better. The cuts look nice and shiny.

So what's the deal with the ugly finish I was getting with carbide? I
think I know why the tips snapped off, but the finish part I don't
understand. A mild steel rod looked awful with the carbide cutter too. It
looked like there was more tearing or smearing than cutting going on.