Step drills are widely used for hole drilling on thin plates under 3mm. 

High-end HSS step drills are fully ground with CBN wheels, which impose higher requirements:

high sharpness and good form retention for CBN wheels.

To meet such demands of step drill manufacturers, our company has developed a dedicated CBN wheel. The processing parameters are as follows:

Machine: Tongchuang TC-W5POWER

CBN Wheels:

• Fluting: 125×31.75×10×14×65° AB107-A-13

• OD Grinding: 125×31.75×10×6.5 AB107-A-13

• Drill Point: 100×31.75×10×6 AB107-A-13

Cooling: Oil cooling

Workpiece: Solid HSS 4241. Max tool diameter 36mm, overall length 58mm, helix angle 60°, 2-flute.

Grinding Process:

• Linear speed: 25 m/s

• Max depth of cut for chip gullet: approx. 6.5 mm (manual measurement error exists)

• Feed rate: 70 mm/min

• Step face grinding stock: 0.30 mm

• First 6 step faces: feed rate 250 mm/min

• Middle 4 step faces: feed rate 220 mm/min

• Last 2 step faces: feed rate 200 mm/min

• Cutting edge & chip gullet: feed rate 120 mm/min

Dressing interval: Dress after every 10 pieces

Total cycle time: 9 min 52 sec