Helical Ramp Angle

Calculate the Z-axis plunge per revolution (Z-Drop) or determine the effective ramp angle to prevent breaking your end mills.

°
Check your tool manufacturer's catalog. Often 1° - 3° for indexable tools.
The Z-axis depth the tool moves per full 360° rotation.
Interpolation Results
Z-Drop Per Revolution

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in
Effective Ramp Angle

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°
Tool Center Path Circumference: -- in
Unwrapping the Helix
θ Path Circumference (C) Z-Drop
The Geometry

When you interpolate a hole, the center of the tool travels in a circle smaller than the hole. The circumference of this center path is:
$C = \pi \times (D_{hole} - D_{tool})$.

If you "unwrap" this path into a straight line, you get a right triangle where the base is the circumference, the height is the Z-Drop, and the slope is the ramp angle.

Why it Matters
  • Insert Damage: Non-center-cutting indexable tools will shatter if you plunge steeper than their rated max angle because the non-cutting center web hits the material.
  • Chip Evacuation: Steeper angles require more chip clearance.