Motor Rotor Drill for Weight-Reduction Holes in Laminated Rotors

In summary, the Motor Rotor Drill solution developed by Aoshiji® Custom Tool has proven highly effective for one of the most challenging operations in new-energy motor rotor manufacturing: drilling weight-reduction holes in laminated silicon-steel rotors under long overhang and dry-cutting conditions. The customer’s component, built from stacked silicon-steel sheets, introduced multiple sources of instability—interlayer gaps causing intermittent impact on the cutting edge, a required 160 mm tool overhang reducing system rigidity, and a dedicated special-purpose machine with limited spindle and fixturing stiffness. Together, these factors made it extremely difficult to maintain tool life, dimensional accuracy, and machining stability with conventional drills.

To address these constraints, Aoshiji® Custom Tool engineered a Motor Rotor Drill featuring a three-flute anti-vibration configuration, optimized cutting-edge geometry, and a reinforced core design. The three-flute layout balances cutting forces and suppresses chatter, enabling stable drilling even at extended tool projection. The refined cutting geometry enhances centering capability and edge toughness, effectively resisting chipping under repeated impact as the tool passes through each silicon-steel layer. At the same time, the strengthened core and carefully tuned web thickness deliver higher rigidity without sacrificing chip evacuation, ensuring smooth chip flow and controlled heat generation in dry-cut conditions.

In parallel, extensive testing of carbide substrates and advanced coating combinations allowed us to select a material–coating system that offers high wear resistance, low friction, and reliable thermal stability. This synergy between tool geometry, core design, and coating technology enables the Motor Rotor Drill to achieve consistent hole quality, longer tool life, and predictable performance, even on lower-precision machines and less-than-ideal clamping setups. For the customer, the result is a robust, repeatable process that reduces unplanned downtime, lowers the risk of scrap, and delivers a more competitive cost per rotor.

For manufacturers facing similar high-precision and long-overhang drilling tasks, Aoshiji® Custom Tool’s portfolio extends beyond Motor Rotor Drills to include Combination Drill & Chamfer Tooland Straight Flute Step Drill – Custom CNC Tool Design solutions for contour finishing and clearance milling in complex structural components. These complementary tools help build a complete process chain around critical rotor and e-mobility parts, ensuring that each operation—from drilling to profiling and deburring—is optimized for stability and efficiency.

As global leaders such as Sandvik Coromant and MAPAL continue to push the boundaries of e-mobility component machining, Aoshiji® Custom Tool remains focused on delivering practical, engineering-driven solutions tailored to real-world production environments. By choosing Aoshiji® Custom Tool’s Motor Rotor Drill for laminated rotor weight-reduction holes, manufacturers gain more than just a special-purpose drill—they gain a proven process solution that enhances rigidity, minimizes vibration, and provides reliable, long-term performance in the precision machining of silicon-steel rotor assemblies.

As highlighted in our previous article, “Case Study | Aoshiji® Custom Tool Composite (Form) Milling Cutter for High-Efficiency Machining of Electromagnetic Valve Cores,” our development philosophy focuses on solving real-world machining challenges through optimized geometry, tailored material selection, and precise engineering support.