Cylindrical helical tooth milling cutters are commonly used in CNC machining for milling planes, grooves, gears, and other surfaces. The milling quality of the cutter blank directly affects the accuracy and service life of the final tool. As the tool blank, the cutter blank is milled to create the basic shape, spiral groove, and end face structures, laying the foundation for subsequent sharpening and heat treatment. The milling of cylindrical helical tooth milling cutter blanks requires high precision and complex shapes. In particular, the lead and helix angle of the spiral groove must be strictly controlled. Therefore, a reasonable processing technology, dedicated fixtures, and precise adjustment methods are required to ensure that the various parameters of the cutter blank meet the design requirements.
The material selection and pretreatment of cylindrical helical tooth milling cutter blanks are crucial to milling performance and final performance. Blanks are typically made of high-speed steel (such as W18Cr4V, W6Mo5Cr4V2) or cemented carbide (such as WC-Co alloy). High-speed steel blanks offer excellent toughness and machinability, making them suitable for manufacturing small and medium-sized milling cutters. Cemented carbide blanks, however, are hard and wear-resistant, but also tend to be brittle, making them suitable for high-speed cutting or CNC machining hard materials. To improve cutting performance and minimize CNC machining distortion, high-speed steel blanks undergo a spheroidizing annealing treatment before milling to spheroidize the carbides and reduce the hardness to 207-255 HBW, enhancing the material’s plasticity and machinability. Cemented carbide blanks undergo pressing and sintering to ensure sufficient density (≥90% of theoretical density) and strength. The forging process ensures that the fiber orientation of the blank is parallel to the axis of the blank to prevent cracking during subsequent processing and use.
The milling process for cylindrical helical tooth milling cutter blanks is carried out in stages, gradually developing the blank’s structural characteristics. A typical process is: blank forging → annealing → rough milling of the outer diameter and end face → center hole drilling → rough milling of the spiral groove → semi-finishing milling of the outer diameter and end face → semi-finishing milling of the spiral groove → finish milling of the end face and shoulder → inspection. The rough milling stage primarily removes the bulk of the stock, leaving a 1-2mm stock on the outer diameter and end face and a 0.5-1mm stock on the spiral groove. High cutting parameters are used during this stage to improve efficiency. The semi-finishing milling stage corrects form errors, bringing all dimensions closer to design requirements in preparation for finish milling. The finish milling stage ensures end face flatness, shoulder perpendicularity, and spiral groove lead accuracy to meet subsequent sharpening requirements. For blanks with larger diameters (>100mm) or larger helix angles (>30°), aging treatment is required after semi-finishing milling to eliminate CNC machining stresses and prevent deformation after finish milling.
Milling the spiral grooves of cylindrical helical tooth milling cutter blanks is a critical step in the CNC machining process, requiring precise helix angle, lead, and groove profile. Spiral groove milling is typically performed on a universal milling machine, with the helix feed achieved by rotating the worktable angle (equal to the helix angle), or by programming helical interpolation on a CNC milling machine. Milling spiral grooves requires the use of a dedicated angle milling cutter or a profile milling cutter. The tool angle must align with the flute angle of the spiral groove (for example, the flute angle for a straight tooth milling cutter is 40°-60°). The tool material used is high-speed steel or carbide. Depending on the blade material, carbide cutters are used for high-speed steel blanks, while diamond cutters are used for carbide blanks. During the milling process, lead accuracy must be maintained through gear calculation or CNC programming, with lead error within ±0.03mm/100mm. The helix angle error must be ≤±10′ and can be checked using a universal angle ruler or sine rule. To ensure the symmetry of the spiral groove, after milling each groove, it is necessary to use the dividing head to accurately index (indexing error ≤ ±5′) before milling the next groove to ensure that the grooves are evenly distributed.
The fixture and adjustment used in milling cylindrical helical tooth milling cutter blanks significantly impact CNC machining accuracy, ensuring the blank’s positioning accuracy and stability. The blank is typically clamped using dual ejector pins, with the center holes at both ends serving as the reference. The center holes are ground to a roundness error of ≤0.01mm, and the coaxiality error of the center holes at both ends is ≤0.02mm, ensuring radial runout of ≤0.03mm during rotation. For blanks without a center hole, a single clamp and a single ejector are used. The clamping portion undergoes rough turning, ensuring the outer diameter has a roundness error of ≤0.02mm and coaxiality with the center hole at the other end is ≤0.03mm. When adjusting the worktable angle, use a sine rule or angle ruler to accurately measure and ensure that the worktable rotation angle is equal to the helix angle of the tool blank, with an angle error of ≤±30″. When adjusting the tool position, ensure that the tool axis and the tool blank axis are in the same plane, with a height difference of ≤0.02mm to avoid skew in the milled spiral groove. When trial cutting, first mill a spiral groove and measure its lead and helix angle. If there is an error, readjust the worktable angle or the pulley parameters until it meets the requirements.
The cutting parameters and quality control for milling cylindrical helical tooth milling cutter blanks require appropriate selection based on the material and processing stage. When CNC machining high-speed steel blanks, use carbide tools (such as YT15) for rough milling at a cutting speed of 80-120 m/min, a feed rate of 0.15-0.25 mm/r, and a depth of cut of 1-2 mm. For fine milling, use high-speed steel tools (such as W18Cr4V) at a cutting speed of 30-50 m/min, a feed rate of 0.05-0.1 mm/r, and a depth of cut of 0.1-0.3 mm. When CNC machining carbide blanks, use diamond tools at a cutting speed of 50-80 m/min, a feed rate of 0.05-0.1 mm/r, and a depth of cut of 0.05-0.1 mm. Use a cooling fluid (such as kerosene) to prevent tool overheating. Quality inspection items include: outer diameter (tolerance ±0.1mm), end face flatness (≤0.02mm), shoulder perpendicularity (≤0.01mm/m), spiral groove lead (tolerance ±0.03mm/100mm), and helix angle (tolerance ±10′). If spiral groove asymmetry is detected, the indexing head accuracy must be checked. If the lead error exceeds tolerance, the gear must be recalculated or the CNC program adjusted. If the groove angle error is excessive, the cutter must be replaced or sharpened. Through strict process control and quality inspection, the CNC machining accuracy of cylindrical helical tooth milling cutter blanks is guaranteed, providing a reliable foundation for subsequent sharpening and use.
