Single-edge external chip removal deep hole drills are also called gun drills because they were originally used to process gun barrels. They are mainly used to process small 

holes with a diameter of 3 to 20 mm, and the ratio of hole depth to diameter can exceed 100. The precision of the processed holes is IT8 to IT10, the surface roughness of the 

processed surface is Ra3.2 to 0.8 μm, and the linearity of the holes is also relatively good.

When the single-edge external chip removal deep hole drill is working, the cutting fluid is sent into the cutting area from the oil inlet holes of the drill rod and the cutting 

part at high pressure (3.4 to 9.8 MPa) to cool and lubricate the drill bit, and the chips are flushed out through the V-shaped grooves of the drill rod and the cutting part, that 

is, the cutting fluid is injected from the drill rod, and the chips are flushed out of the drill rod, so it is called external chip removal.

The cutting part and the drill rod are generally welded together. The drill rod is usually rolled out with a V-shaped chip removal groove using a seamless steel pipe. Under the 

condition of ensuring sufficient strength and rigidity of the drill rod, the inner diameter of the drill rod should be as large as possible to facilitate cooling, lubrication and chip 

removal of the cutting part. To avoid friction between the drill rod and the hole wall or drill sleeve, the outer diameter of the drill rod should be slightly smaller than the outer 

diameter of the drill bit by 0.5 to 1 mm. The cutting part can be made of high-speed steel or cemented carbide.

The biggest feature of the cutting part of the single-edge external chip removal deep hole drill is that there is no transverse edge, and there is only a cutting edge on one 

side of the axis. The cutting edge is divided into inner and outer edges, and its main deflection angle is κr1 and κr2, and the drill tip deviates from the axis centerline by a 

distance e. During the processing, the radial force acting on the outer edge is greater than the radial force acting on the inner edge, so that the radial force of the drill bit can 

always act on the surface to be processed during the drilling process, and at the same time ensure that the drill bit is close to the larger side of the support surface to ensure 

the linearity of the processed hole.