Gun Drill Runout: How Tool Runout Affects Hole Size, Roundness, and Straightness
Runout is one of those problems that is easy to ignore because the symptoms look like other issues. A hole comes out 0.03mm oversize and the natural instinct is to check the drill diameter or the bushing clearance. Half the time, the culprit is tool runout. Here is what I have learned about measuring runout, understanding its effects, and controlling it. What Runout Actually Does to the Hole When a gun drill has runout at the tip, the cutting edge orbits around the spindle centerline instead of rotating on-axis. This orbit increases the effective cutting diameter. ...