Grinding Parameters of CBN Wheels for HSS Step Drills

Step drills are commonly used for drilling holes on thin plates with a thickness less than 3 mm. High-end high-speed steel (HSS) step drills are fully ground with CBN grinding wheels, which imposes stricter standards on CBN wheels: outstanding sharpness and excellent profile retention.

To satisfy the production needs of step drill manufacturers, our company has specially developed a dedicated CBN grinding wheel. The detailed processing parameters are listed as follows:

Equipment: Tongchuang TC-W5POWER CNC Grinding Machine

Grinding Wheel Specifications:

• Flute Grooving Wheel: 125×31.75×10×14×65°, Grade AB107-A-13
• Outer Circle Grinding Wheel: 125×31.75×10×6.5, Grade AB107-A-13
• Drill Point Grinding Wheel: 100×31.75×10×6, Grade AB107-A-13

Cooling Mode: Oil Cooling

Workpiece Information:

• Material: Solid HSS 4241
• Maximum tool diameter: 36 mm
• Total tool length: 58 mm
• Helix angle: 60°
• Number of cutting edges: 2 flutes

Grinding Process Parameters:

• Peripheral linear speed: 25 m/s
• Maximum grinding depth for chip flutes: approximately 6.5 mm (with permissible error from manual measurement), feed rate: 70 mm/min
• Stock removal for step face grinding: 0.03 mm (30 μm)
• Feed rate for the first 6 step faces: 250 mm/min
• Feed rate for the middle 4 step faces: 220 mm/min
• Feed rate for the last 2 step faces: 200 mm/min
• Feed rate for end tooth and chip flute grinding: 120 mm/min

Dressing Cycle: Dress the grinding wheel after grinding 10 drills

Total Machining Duration: 9 minutes and 52 seconds