Hey all- So I have done this job for a customer multiple times and just have never really gotten it right. Thought i would throw this on here and see if i could get some suggestions.

I'm drilling a series (300 holes) #36 in a long (6') SS tube 1 1/2" OD 1/8" wall. 3 Tubes actually. I am currently using some machine length cobalt steel #36 drill bits. I've tried using a center drill, i've tried no center drill. I've tried different depths on the center drill. I've tried different feeds and speeds. sometimes I'll get 150 holes no problem. Sometimes i'll get 300 holes no problem. sometimes i'll get 10 holes and my drill bit will break. I just can't seems to get any sort of consistency. It seems like when I center drill then the drill bit chatters really bad getting past the center drilled hole. if i don't center drill the bit will walk sometimes. I am just curious what you guys would recommend? Center drill or no? Speeds and feeds? anything to help.... I don't do a lot of stainless steel so whenever i make changes i'm just taking a shot in the dark.

What I am around for S & F I got from "Machinst Toolbox" and is roughly 1300rpm @ 3.5ipm

Thanks for the help!!
-Nate