Single-edged gun drill (hereinafter referred to as gun drill) is used to process deep holes with a diameter of Φ1～40mm and a length-to-diameter ratio of 100～250 times. It is currently the only method for processing small diameter deep holes with a diameter of Φ1～6mm. The accuracy of machining holes can be stabilized at IT 8～10, and individual ones can reach IT6～7; the surface roughness can be stabilized at Ra12.5～3.2μm (▽3～▽5), and individual ones can reach Ra0.8～ 0.4μm (▽7～▽8), the straightness of the hole can reach 0.05mm/m. Gun drills have a wide range of applications. In addition to processing ordinary steel materials and castings, they can also process soft metals, alloy steels, stainless steels, and heat-resistant steels.