The Method of Hob Computation

Normal pitch=Mn x Π（Mn: Normal Module)

Axial pitch=Mn/cos LA

Lead=Axial pitch x Number of start

LA(Lead Angle)=sin-1(Mn x Number of start/Hob PCD)

Cam amount(relief amount)=Hob OD x Π x tan(cam angle)/Hob NT

Cam angle: Generally PA20°-10°， 14.5°-12°，25°-9°

Groove Lead=Hob PCD x Π/tan LA

Flute depth= Total tooth height if a hob+ Cam amount+1.5mm

Hob's Relief Angle=tan-1(tan PA x tan Cam angle)