Characteristics and applications of gun drills in deep hole drilling

The gun drill is an effective tool for deep hole machining in a wide range of applications, from plastics such as fiberglass and Teflon to high-strength alloys.

Features

Gundrills are characterized by good accuracy and low surface roughness in a single pass. Gun drilling is more suitable for small-diameter holes, and usually, holes with a diameter of less than 10mm are more appropriately processed by gun drilling. The most favorable thing is that it can make the iron chips smoothly discharged.

Summarized as follows:

The hole depth and diameter are relatively large, the drilling rod is thin and long, the rigidity is poor, and it is easy to produce deflection and vibration when working. Hole accuracy and surface quality are also difficult to control.

There are a lot of chips and the chip discharge channel is long, so the chip discharge is not good, and it is easy to be clogged and broken.

The drill bit is working in a nearly closed state, and for a long time, the heat is not easy to dissipate, the drill bit is very easy to wear.

Structure

Gun drills are composed of a gun head, a gun barrel and a drill shank. The gun head is usually made of cemented carbide material, the barrel is made of high strength alloy tube, and the shank is the part that connects the drill with the machine tool. Gun drills have two main cutting edges and one sub-cutting edge, the one near the center of the drill is called the inner edge, the other is called the outer edge, and its intersection is called the drill tip.

Application

Since the drill center is off-center, the gun drill is not self-centering and therefore requires the use of a drill sleeve or pilot hole for plunge cuts. When using a drill sleeve, the appropriate size must be selected and the clearance between the sleeve and the head of the gun drill must be maintained between 0.003mm and 0.008mm.

The drilling sleeve used must be wear-resistant and of high hardness; it is generally made of cemented carbide or high-alloyed tool steel, with a hardness of 63-65 HRC; the manufacturing precision of the gun drilling sleeve must be high, with a general surface roughness of the inner hole of Ra1.6-3.2, a coaxiality of the inner and outer diameters of 0.002mm, and an end face runout of 0.005mm.

The distance between the bottom surface of the drilling sleeve and the surface of the workpiece is not more than 0.5mm or the drilling sleeve is close to the surface of the workpiece.