High-Pressure Cooling System for Deep Hole Drilling What are the challenges of deep-hole machining? What types of deep-hole drill bits are available, and what factors should be considered when selecting and choosing a deep-hole drill bit? What are the machining methods for high-pressure coolant systems in deep-hole drilling, and how many precautions should be taken during deep-hole machining? This article covers all of these topics—hopefully it will be helpful to you!

　　. High-Pressure Cooling System for Deep Hole Drilling Challenges in Deep Hole Machining

　　The tool shank is constrained by the bore diameter, resulting in a small diameter, considerable length, poor stiffness, and low strength. During cutting, this easily leads to vibration, surface waviness, and tapering, which in turn adversely affect the straightness and surface roughness of deep holes.

　　During drilling and reaming, if special protective devices are not employed to deliver the cutting fluid, it is difficult to supply the coolant-lubricant to the cutting zone, which diminishes its beneficial effects on tool life and performance and also makes chip evacuation challenging.

　　In deep-hole machining, the cutting condition of the tool cannot be observed directly. Operators must rely on experience to interpret the cutting sounds, inspect the chips, feel the machine vibrations, monitor the workpiece temperature, and check the machine instruments (such as pressure gauges and ammeters) to determine whether the cutting process is proceeding normally.

　　Due to the difficulty in chip evacuation, reliable measures must be implemented to break the chips, control their length and shape, ensure smooth chip removal, and prevent chip jamming.

　　Additional internal (or external) chip-removal devices, guiding and supporting mechanisms, and high-pressure cooling-lubrication systems are installed to ensure smooth deep-hole machining and meet the required machining quality standards.

　　Poor tool cooling leads to elevated cutting temperatures and reduced tool life.

　　. Types of deep-hole drill bits, scope of use and management, and basic operating principles

　　Deep-hole drill bits are classified into two types: external-deck-type and internal-deck-type. External-deck-type bits include gun-body drills and solid carbide deep-hole drills (which can be further divided into those with cooling holes and those without).

　　Internal chip evacuation is categorized into three types: BTA deep-hole drills, jet drills, and DF-system deep-hole drills. The types of deep-hole drills and their respective application and management scopes are shown in the data presented in the figure below.

　　Precautions for High-Pressure Cooling Systems in Deep-Hole Drilling

　　(1) Key operational considerations for deep-hole machining: The coaxial alignment of the spindle, tool guide rails, tool-holder support sleeve, and workpiece support sleeve must meet the specified tolerances. The cutting-fluid system must be functioning properly, and the machined end face of the workpiece should be free of center holes. Drilling on inclined surfaces is prohibited; chip morphology must remain normal to prevent the formation of straight, ribbon-like chips; when machining through-holes at high speeds, decelerate or stop just before the drill bit breaks through the workpiece to avoid damage to the drill.

　　(2) Deep-hole machining and cutting fluids: In the production process management of deep-hole machining, substantial cutting heat is continuously generated and difficult to dissipate, necessitating a cutting-fluid lubrication and cooling system with sufficiently high supply capacity to effectively cool the cutting tool. Typically, a 1:100 emulsion or an extreme-pressure emulsion may be used; when high-precision machining methods are required to achieve superior surface quality or when machining ductile materials, an extreme-pressure emulsion or a high-concentration extreme-pressure emulsion is recommended. The kinematic viscosity of cutting oil generally ranges from 40 to 100–20 cm²/s, with a cutting-fluid flow rate of 15–18 m/s; for smaller diameters, lower-viscosity cutting oils should be employed. For deep-hole machining that demands high dimensional accuracy, a cutting-oil formulation of 40% extreme-pressure sulfurized oil, 40% kerosene, and 20% chlorinated paraffin may be selected. The pressure and flow rate of the cutting fluid are closely related to the hole diameter and the specific machining method, as illustrated in the figure. (3) To ensure the service life of the cutting tool, an automatic-feed tool should be used.

　　When the guide components of the fluid delivery unit and the movable center support bracket are worn, replace them promptly to prevent any adverse impact on drill bit accuracy.

　　Deep-hole machining is a tool-driven manufacturing sector designed for applications in existing technologies, with numerous studies involving diverse industries.

　　The above outlines the key considerations for high-pressure cooling systems in deep-hole drilling, as well as the design’s versatility. For more information, please feel free to contact us at any time! Our company has many years of experience and looks forward to welcoming you aboard.