Are they split point? Do they have an "S" point to self center? I use a stub drill to make a hole 3 diameters deep, then switch to a taper length parabolic flute with a lot of coolant for stainless, or lubricant for aluminum. If you start a hole with a stub drill, the hole acts as a bushing to stop chatter.
Also consider mounting a morse taper block to your tool holder for the drill chuck so the machine can feed the drill more acurately, or get split sleeves that match the taper size and drill size. |