Tool-Geometry

I used to think chip breaking was entirely about feed rate. If the chips were too long, I increased the feed until they broke. That works up to a point, but the drill’s chip breaker geometry sets the baseline for what feed rate will work. Understanding chip breaker geometry helps you choose the right drill for the material and know whether a regrind is maintaining the correct geometry. What a Chip Breaker Does A chip breaker is a groove or step ground into the rake face of the gun drill tip, just behind the cutting edge. As the chip slides across the rake face, it hits the chip breaker and curls. The curl creates bending stress in the chip, and when that stress exceeds the material’s fracture limit, the chip breaks. ...

If there is one thing I have learned across years of running gun drills in production, it is this: tip geometry is everything. You can have the best coolant system, the tightest bushing alignment, and the most rigid machine on the floor, but if the tip geometry is wrong the drill will chatter, wear prematurely, or produce scrap. This article is the practical breakdown I wish someone had handed me when I started — what each angle does, why it matters, and how to set it for the material in the spindle. ...