Center Drills Table of recommend centering condition

Center Drills are the tool for making center hole. Center Drills are also used for positioning before drilling, and for chamfering of the hole. ■Table of recommend centering condition.

HSS (PE-Q PE-90˚)

Work Soft structural steels Carbon steels Alloy steels Stainless steels Aluminum alloy casting

■Names of each part Shank portion Countersink portion material

Drill diam. (Dc) Drill portion Cutting speed

Diameter Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution (Ds) Drill length (ℓ) Overall length (L)

■Shape of center hole and center

Type A (60°) Center hole & 60°center Type B (60°) Center hole & 60°center Type A (90°) Center hole & 90°center

■Advantage of Type B Center holes

Type R Center hole & 60°center

HSS+TiCN (PE-Q-V PE-90˚)

Work Soft structural steels Carbon steels Alloy steels Thermal refined steels Stainless steels Aluminum alloy casting

material Cutting speed Diameter Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution

Avoid scar or distortion resulting from a blow

Note : Advantage of Type B center holes : B type center drill protect the 60° conical bearing surface from scar or distortion resulting from a blow, roughness of workpiece surface or burrs around the hole. Carbide+TiAIN (C-PE-Q-V PE-90˚)

WorkSoft structural steelsCarbon steelsAlloy steelsThermal refined steelsStainless steelsAluminum alloy casting
■Advantage of Type R Center holesmaterial
Cutting speed

Angle of center hole is higher than Angle of center hole is lower than Center hole and center are misaligned.

that of center. that of center. Diameter Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution Revolution Speed Feed per revolution

A type

R type

Technical Inf Note : R type center hole stably holds the center. It also some of advantage of B type center hole.

1. Above condition done by Water Soluble oil. 2. 20% lower feed is recommended when centering process to inclined plane. 3. 20% lower feed is recommended in the case of long shank point drills.