Tooling

The guide bushing supports the gun drill at the entry point of the workpiece. It prevents the drill from whipping or deflecting during the first few millimeters of engagement, which are the most critical for hole straightness. I have spent years selecting and maintaining guide bushings for different applications, and the right bushing choice is one of the most important tooling decisions in deep hole drilling. Guide Bushing Material Selection The most common bushing material is hardened tool steel, typically A2 or D2 tool steel hardened to 58 to 62 HRC. It provides good wear resistance at moderate cost. For high production or abrasive materials, I use carbide bushings. For soft materials where marking is a concern, I use bronze bushings. ...

The guide bushing is one of those parts that nobody thinks about until the holes start coming out wrong. It’s a simple component — a precision-ground tube that supports the gun drill at the entry point. But when it’s worn or incorrectly sized, it causes more problems than any other single component I’ve dealt with. What a Guide Bushing Does The guide bushing supports the gun drill right where it enters the workpiece. The drill passes through the bushing before contacting the material. The bushing prevents the drill from whipping or wandering during the first few millimeters of engagement. ...

Gun drills are precision cutting tools. They have a carbide tip, a long slender shank, and a critical cutting geometry. Improper storage damages the drill and reduces its life. Here’s what I’ve learned about storing gun drills. Storage Racks Gun drills should be stored horizontally in dedicated racks. The rack supports the drill along its full length to prevent sagging. The rack should have individual slots for each drill with a V-groove or U-groove that supports the drill shank. The drill should not contact other drills in the rack. ...