I've got an 8mm diameter hole that is 2.5 inches deep to drill / bore on my lathe. Right now I have been running an 8mm drill with a pecking cycle. The peck retracts all the way to allow coolant to flush the bore. It is difficult to fit a boring bar that deep into a part at that ID. Right now the peck goes 1.0 inches, dwells for 1 second (the drill chatters a bit), retracts then does it again. I am not starting the hole with a center drill, but I do face the part first to give it a flat surface.
I have tried faster spindle rotation with the same feeds and peck depth and the problem got worse.
I was thinking of center drilling with a stubby drill, decreasing the peck depth, decreasing the spindle speed and feed rate. Any other suggestions? How do gun drillers do this with a smaller hole that is 15" or more long!? That's art! I gotta get this hole figured out - it seems easy in comparison to what I know is possible.
I have tried faster spindle rotation with the same feeds and peck depth and the problem got worse.
I was thinking of center drilling with a stubby drill, decreasing the peck depth, decreasing the spindle speed and feed rate. Any other suggestions? How do gun drillers do this with a smaller hole that is 15" or more long!? That's art! I gotta get this hole figured out - it seems easy in comparison to what I know is possible.