centering

[modelman]

I have heard that 135-degree split point drills do not require center drilling. Is this true? Also I cut mostly alum. on my lathe and it seems to cut better with the tool .020" above center. Does this make any sense? If so-why.

[tc1cat]

Not sure about the 135-degree point drills. Always use c'drills except for the Titex drills in both the lathe and mill.
Tool above center might be due to rake of the tool. Are you using ground tooling or carbide insert tooling? I have some insert tooling that my Sherline lathe wouldn't cut air with. No idea why as they work great in other machines.
I see that pugs beat me to answering!

Lynn