The geometric design of a brazing hole drill is a key factor in determining chip evacuation effectiveness. Parameters such as the helix angle, edge angle, rake angle, relief angle, and chisel edge bevel work together to directly influence chip formation, flow, and evacuation efficiency. Proper configuration of these angles not only improves machining efficiency but also extends drill bit life, reducing damage and quality issues caused by chip clogging.
The helix angle, a key parameter of a brazing hole drill, directly influences chip curling and evacuation. A larger helix angle increases the space in the spiral flutes, providing more ample storage and transport channels for chips. Once formed, chips are quickly evacuated along the spiral flutes, avoiding accumulation in the drilling area. Furthermore, the coupled relationship between the helix angle and rake angle determines the sharpness of the cutting edge: As the helix angle increases at the outer edge, the rake angle increases, resulting in smoother cutting and more easily broken chips. Meanwhile, as the helix angle decreases at the core, the rake angle may become negative. While this enhances cutting edge strength, it requires compensating for chip evacuation performance through other angles.
The edge angle influences chip evacuation stability by adjusting the cutting force distribution. A larger rake angle allows the cutting edge to more easily penetrate the workpiece, increasing cutting thickness and width. However, this can increase cutting forces and, if the chip evacuation channel is improperly designed, can easily lead to chip blockage. Conversely, a smaller rake angle reduces cutting forces, but may result in excessively long chips due to insufficient cutting efficiency, making chip evacuation more difficult. Therefore, rake angle design must balance cutting forces and chip evacuation requirements based on material properties. For example, when machining high-hardness materials, an appropriate increase in the rake angle can disperse cutting forces while optimizing the chip flute structure to ensure smooth chip evacuation.
The rake angle distribution plays a decisive role in chip morphology and evacuation resistance. A larger rake angle at the outer edge creates a sharper cutting edge, minimizes chip deformation, and facilitates curling and evacuation. However, a negative rake angle at the core can increase cutting resistance and cause chips to stick. By nonlinearly coupling the helix angle, lead angle, and rake angle, it is possible to optimize the rake angle distribution, achieving rapid chip breakage at the outer edge and controlled chip evacuation from the core. For example, a negative rake angle design can direct chips toward the machined surface, reducing accumulation in the drilled area while enhancing the core's ability to withstand axial loads.
Clearance angle design requires a balance between friction reduction and cutting edge strength. An appropriately large clearance angle reduces friction between the tool's flank and the workpiece, allowing cutting fluid to more easily reach the cutting zone, reducing cutting heat and facilitating chip evacuation. However, an excessively large clearance angle can weaken cutting edge strength, causing vibration and tool jamming, which in turn hinders chip evacuation. Therefore, clearance angle design must be tailored to material characteristics. For example, a smaller clearance angle is recommended to maintain structural rigidity when machining soft materials, while a larger clearance angle is recommended to reduce friction when machining hard materials.
The chisel edge rake angle plays a critical role in drill centering and initial chip evacuation. A larger chisel edge rake angle allows the chisel edge to more easily engage the workpiece, reducing deflection and wobble during the drill's start, ensuring that chips are evacuated in the intended direction from the outset. Furthermore, the chisel edge rake angle and clearance angle must be designed in tandem to avoid excessive clearance angles leading to excessively small chisel edge angles, which can result in poor centering and chip evacuation. Optimizing the chisel edge rake angle significantly improves holemaking accuracy and reduces hole diameter deviations caused by chip evacuation issues.
The brazing process is crucial for geometric stability. During high-temperature brazing, insufficient bonding strength between the brazing filler metal and the substrate and diamond abrasive can cause the drill bit's geometry to deform under cutting forces, compromising chip evacuation. Therefore, optimizing the filler metal composition and brazing temperature is crucial to ensure long-term geometric stability. For example, using nickel-based alloy brazing and high-temperature vacuum brazing techniques can enhance drill bit structural rigidity and reduce chip evacuation obstacles caused by angular deformation.
The geometric design of a brazing hole drill requires comprehensive consideration of cutting mechanics, material properties, and process stability. Systematic optimization of the helix angle, cutting edge angle, rake angle, relief angle, and chisel edge bevel angle can achieve efficient chip formation and smooth evacuation, significantly improving machining efficiency and quality. In the future, combining cutting simulation with machine learning technologies will further refine geometric design and provide technical support for the application of brazing hole drills in complex machining scenarios.
