Tool-Inspection

Not all regrinds are equal. I have learned the hard way that a bad regrind will cost you a broken drill and a scrapped part. A gun drill costs hundreds of dollars to replace, but a scrapped aerospace part can cost thousands. I inspect every reground drill before it goes into the spindle, and I reject about one in five regrinds from even my best sharpening vendors. Here is my inspection routine. It takes ten minutes and has saved me from countless spindle crashes, broken drills, and rejected parts. ...

Why Post-Regrind Inspection Matters I measure every reground gun drill before it goes back into production. Incorrect regrind geometry is one of the most common causes of poor hole quality that I see. The regrind operator might be having a bad day, the grinding wheel might have dulled mid-cycle, or the fixture might have moved. The measurement catches these errors before the tool goes into a part. A gun drill with incorrect geometry cuts poorly from the first revolution. It will produce rough surface finish, oversized bores, or excessive burrs. In some cases, it will break within the first few millimeters of cut. The inspection takes 2-3 minutes and saves hours of troubleshooting time. ...

Gun drills are precision tools that are surprisingly easy to damage. The long, slender shank and the exposed carbide tip are vulnerable to handling damage. I’ve seen good drills ruined by careless handling. Here’s how to prevent damage and what to inspect for. Common Damage Modes Bent shank. The most common damage. A gun drill that’s dropped or handled roughly has a bent shank. Even a slight bend causes runout. ...