Gun Drill Regrinding: When and How
Regrinding a gun drill requires precision. The angles on the tip determine how the drill cuts, how chips form, and how the tool wears. Getting them wrong means poor hole quality and short tool life. Here is the procedure I use. When to Regrind I regrind a gun drill when any of these conditions are met: Surface finish degrades beyond spec Cutting forces increase noticeably (spindle load rises 20%+) Flank wear exceeds 0.2mm on the primary clearance Corner wear exceeds 0.1mm Chips change from short broken segments to long stringy ribbons For production work, I track holes per regrind and schedule regrinds at a fixed interval. For most steel applications, this is 150-250 holes per regrind depending on diameter and material. ...