First-Time

I have had this conversation a dozen times. A shop calls and says they tried gun drilling on a manual lathe, snapped the drill in the first hole, and want to know what went wrong. The answer is almost always the same: coolant pressure, pilot hole, or feed rate. Sometimes all three. Here is what I see most often. Failure 1: Not Enough Coolant Pressure This is the #1 first-time killer. A standard lathe coolant pump puts out 20-50 psi. Gun drilling needs 500-3000 psi depending on diameter. The difference is not subtle — at 50 psi, chips do not move. They pack behind the drill and the torque spikes until something breaks. ...

Every deep hole driller remembers their first breakage. It’s like a rite of passage — one of those moments that divides your career into “before” and “after.” Before the break, you think you know what you’re doing. After the break, you know how much you don’t know. Mine happened in the fall of 2008, on a Tuesday morning that started like any other. I was twenty-four years old and had been running deep hole drills for about a year. I thought I had it figured out. I’d done a hundred jobs by then, maybe more. I’d changed drills, adjusted feeds, swapped guide bushings, and read chips like a pro. The senior guys had stopped hovering over my shoulder, which I took as a sign that I’d arrived. ...