In the machining process of a brazing hole drill, the design of the chip removal structure directly affects the chip removal efficiency and drilling quality. If chips cannot be removed in time, they can easily clog the cutting grooves, leading to decreased drilling accuracy, shortened lifespan of the brazing hole drill, or even breakage. Therefore, optimizing the chip removal structure requires comprehensive improvements from multiple dimensions, including cutting groove geometry, chip breaking design, coolant assistance, material selection, chip groove morphology, brazing hole drill rigidity, and process parameter adaptation, to reduce the risk of clogging.
The geometry of the cutting grooves is fundamental to chip removal. A reasonable design of the cutting groove helix angle and width can significantly improve chip removal efficiency. An excessively large or small helix angle is detrimental to chip removal: if too large, chips may remain in the cutting groove due to insufficient centrifugal force; if too small, increased friction between the chips and the hole wall may cause clogging. Typically, the helix angle needs to be adjusted according to the characteristics of the material being machined. For example, a smaller helix angle is used when machining brittle materials to promote chip breakage, while a larger helix angle is used when machining tough materials to enhance chip removal power. Meanwhile, the width of the cutting groove must match the chip morphology to avoid excessive narrowness leading to chip accumulation or excessive width reducing the rigidity of the brazing hole drill.
Chip breaking design is key to reducing long chip entanglement. By adding chip breaking edges or re-grinding chip dividers in the cutting groove, long chips can be broken into short fragments, reducing the risk of clogging. For example, a stepped chip breaking edge can be designed in the brazing hole drill groove, causing chips to break due to uneven stress during flow; or an asymmetrical chip divider can be used to break wide chips into multiple narrow chips for easier removal. Furthermore, re-grinding the chisel edge can reduce axial force, preventing chips from deforming and clogging the cutting groove due to compression.
The auxiliary role of coolant cannot be ignored. Coolant not only lowers the cutting temperature but also uses impact force to eject chips from the cutting groove. Optimizing the coolant supply method, such as using a high-pressure internal cooling system that sprays coolant directly into the cutting zone, can significantly improve chip removal efficiency. Meanwhile, the viscosity and flow rate of the coolant must be matched to the machining conditions: high-viscosity coolants are suitable for heavy-duty machining, but it is necessary to prevent chip adhesion due to poor flowability; low-viscosity coolants require sufficient flow to create a continuous scouring force.
Material selection directly affects the durability of the chip removal structure. The brazing layer must use high-strength, high-wear-resistant alloy materials, such as nickel-based or cobalt-based brazing filler metals, to ensure that the cutting groove shape remains stable under high temperature and high pressure environments. Simultaneously, the base material must have good thermal conductivity, such as alloy steel or cemented carbide, to quickly dissipate cutting heat and prevent chips from softening and adhering to the cutting groove. Furthermore, surface coating technology can further reduce friction between chips and the cutting groove; for example, using titanium nitride (TiN) or chromium nitride (CrN) coatings can reduce the tendency for chip adhesion.
Optimizing the shape of the chip removal groove must balance rigidity and chip removal efficiency. Traditional straight chip removal grooves are prone to clogging due to chip accumulation, while spiral or curved chip removal grooves can reduce the risk of clogging by changing the direction of chip flow. For example, using variable helix angle chip evacuation grooves allows chips to automatically break during evacuation due to changes in the helix angle; or designing a double chip evacuation groove structure increases the chip removal channel area and improves chip removal capacity. Furthermore, the depth and bottom diameter of the chip evacuation grooves must be properly matched to avoid excessive depth leading to decreased rigidity of the brazing hole drill or insufficient depth affecting chip removal efficiency.
Strengthening the rigidity of the brazing hole drill is an indirect means of reducing clogging. By optimizing the structural design of the brazing hole drill, such as increasing the core thickness or using a segmented drill body, the overall rigidity of the brazing hole drill can be improved, reducing vibration and deformation during machining. Vibration causes frequent changes in the relative position of the cutting groove and the chip, increasing the risk of clogging; while insufficient rigidity may cause the brazing hole drill to shift, leading to excessive friction between the chip and the hole wall and clogging. Therefore, strengthening rigidity not only improves drilling accuracy but also indirectly improves chip removal efficiency.
Adapting process parameters is the final hurdle in chip removal optimization. A proper match between feed rate, spindle speed, and depth of cut ensures that the chip morphology is compatible with the chip removal structure. For example, increasing the feed rate can thicken the chips and reduce the generation of fine chips; increasing the rotational speed can enhance centrifugal force and promote chip removal. However, it is important to note that parameter adjustments must not exceed the brazing hole drill's load-bearing capacity; otherwise, excessive cutting force may cause the brazing hole drill to break. In actual operation, the optimal parameter range needs to be determined through trial cuts and dynamically adjusted according to the characteristics of the material being processed.
