Coatings

I use TiAlN-coated carbide for steel and DLC for aluminum. That combination covers about 80% of what I drill. The tool material and coating are critical for gun drill performance. Get the combination wrong and the drill wears fast, holes drift, or surfaces come out rough. I have tested enough bad combinations to have a strong opinion on what works. Tool Material Options Carbide Grades Most gun drills use carbide. It offers the best balance of wear resistance and toughness. ...

I select gun drill geometry based on the material I’m cutting. In my experience, the geometry is the single biggest factor determining whether a job runs smoothly or produces scrap. I have seen shops spend thousands on premium carbide drills only to get poor results because the geometry was wrong for the material. The geometry of a gun drill’s cutting tip determines how the drill performs. Different geometries are suited to different materials and applications. ...