The oil passage cooling tool holder, also known as the Internal Cooling Tool Holder, is a type of tool holder with precisely designed internal channels. It can accurately and leak-free deliver the high-pressure coolant (usually an oil-water emulsion) pumped by the machine tool directly to the cutting edge, fundamentally changing the traditional "spraying" cooling method.
I. Working Principle of the Internal Cooling Tool Holder
1. Pressure supply: The high-pressure cooling pump of the machine tool (usually requiring a pressure of 70 bar or more, and in modern systems, it is common to have 100-200 bar, or even higher) generates high-pressure cooling fluid.
2. Sealed transmission: The coolant flows through the internal passage of the machine tool's main shaft and reaches the nose end of the main shaft. The internal cooling holder forms a tight connection with the main shaft end face through a precise sealing ring (such as an O-ring, piston ring or special curved surface seal) at its rear part, preventing high-pressure coolant from leaking at the connection point.
3. Internal flow diversion: High-pressure coolant enters the pre-embedded, dynamically balanced small channels inside the tool handle.
4. Precise Jetting: The coolant finally passes through the nozzle at the front end of the tool handle or is channeled into a specific angle, and is then sprayed at an extremely high speed onto the area where the cutting edge of the tool comes into contact with the chips and the workpiece at the very moment.
II. Advantages and Features of the Internal Cooling Holder
1. Cooling effect: Traditional external cooling cannot penetrate into the high-temperature area at the tip of the tool. Internal cooling directly "sprays" the coolant onto the hot spot, which can instantly remove the cutting heat and effectively lower the temperature at the tool tip. This is the most effective method to prevent the tool material (especially hard alloys and metal ceramics) from softening and spreading wear due to high temperature.
2. Chip removal capability: The high-pressure coolant can function like a "high-pressure water gun", promptly flushing away the generated chips from the processing area. This is particularly crucial for deep hole machining (such as drilling deep holes and milling deep cavities), as it effectively prevents problems such as chip entanglement, scratching of the already machined surface, and even the clogging and breaking of the tool due to poor chip removal.
3. Processing quality and efficiency: Better cooling and chip removal have resulted in a more stable cutting process, enabling higher dimensional accuracy and surface finish. Due to the extended tool life, the number of tool changes is reduced, and more aggressive cutting parameters can be adopted, thereby significantly increasing the metal removal rate (MRR) and overall production efficiency.
III. Application Scenarios of the Internal Cooling Holder
The application of the internal cooling holder is very extensive, especially in the following fields:
1. Deep hole drilling: This is the most classic application of the oil path tool holder. The high-pressure coolant is responsible for cooling, lubricating and forcibly pushing the long chips out of the hole.
2. Deep cavity milling (especially for deep cavities): In the mold industry, this technique is used to mill complex deep cavities, ensuring that the chips at the bottom corners can be effectively removed.
3. Efficient milling and high-speed milling: The removal of high-strength materials generates a large amount of heat, and internal cooling is a necessary condition for maintaining stable processing over a long period.
4. Hybrid Machining Center: On a machining center with a power tool turret, the rotating tool also requires internal cooling support during milling and drilling operations.
5. Processing of difficult-to-machine materials: As mentioned earlier, these materials are indispensable in the manufacturing of aerospace and energy equipment (such as turbine blades and engine parts).
6. Thread Milling: Ensure the quality and accuracy of the thread profile.
IV. Limitations and Precautions of the Internal Cooling Holder
1. High cost: The oil path tool handle itself, the corresponding high-pressure cooling pump, the filtration system, and the maintenance of seals all require significant investment.
2. System complexity: The machine tool needs to have an internal cooling function (or be modified to add a rotary joint), and extremely high cleanliness standards must be met for the cooling fluid. Even the slightest impurities could clog the precise internal cooling channels.
3. Not universally applicable: For the routine processing of ordinary steel and cast iron, external cooling is often sufficient. Using internal cooling might increase unnecessary costs.
V. Summary
The internal cooling tool holder is the "power multiplier" of the modern high-performance processing system. By precisely applying high-pressure coolant to the core area of the cutting edge, it solves the three key problems of cooling, chip removal, and lubrication, thereby performing exceptionally well in terms of efficiency, quality, and tool life. For mechanical processing enterprises that deal with difficult-to-machine materials, deep-hole processing, and strive for the highest production efficiency, investing in a mature oil circuit toolholder system is a very valuable choice.
Post time: Sep-04-2025
