HSS drills - black or silver?

All HSS is silver , highly heat treated and very hard .

China makes forged , black bits they call HSS . Much more brittle and not as tough as HSS . HF sells them and sometimes T.I.N. coated . ________________________________

Jordan wrote:

Go to mcmaster and read about drill bit finishes it explains them great

Thanks. Looks like polished is good for ferrous and non-ferrous, but black not recommended for non-ferrous metals. Well, I've used them on aluminium and they seem to work OK.

Some of my black drills are Czech and German, marked HSS.

Jordan

They work fine, but tend to allow streaking and chip welding of the parent metal. It can be the source of considerable irritation if you're drilling soft aluminum, but, like you, I use them that way all the time. Lubrication works wonders towards limiting such problems.

Harold