"Alex" wrote in message
ups.com...

Can anyone explain what exactly the difference is?


Alex,

If you can get you hands on some tool or alloy steel, you'll see the
difference rapidly. Mild steel and many common non-ferrous materials are
very forgiving. If you run your cheap bits conservatively in these
materials, you probably won't have trouble. Industry however has no time for
"conservatively" and we don't get to choose the "forgiving" materials so
good bits that don't get dull after one hole in D2 are a requirement.

Regards,

Robin