—Helix angle is the angle between the leading edge of the
land and the axis of the drill. Sometimes it is also called as spiral angle.
—The helix results in a positive cutting rake
—This angle is equivalent to back rake angle of a single
point cutting tool.
— Usual – 20° to 35° – most common
— Large helix : 45° to 60° suitable for deep holes and
softer work materials
— Small helix : for harder / stronger materials
— Zero helix : spade drills for high production drilling
micro-drilling and hard work materials
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