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Rotary Feedrate Calculator

Convert linear feed (in/min or mm/min) to rotary feed (°/min) and evaluate simultaneous rotary+linear motion feedrates. Includes charting, CSV export, and a safety indicator.

How to use

  1. Select units (Inch or Metric).
  2. Choose a mode: Rotary Only or Rotary + Linear.
  3. Enter parameters and click Calculate.
  4. Review the result, safety indicator, and the chart.

💡 Quick Tips

  • Double-check diameter/radius inputs — small changes strongly affect °/min.
  • Set Machine Max to your actual rotary axis limit (°/min).
  • If feedrate exceeds max, reduce linear feed or increase diameter/radius.

⚙️ Example: Milling a 20mm Diameter Hole

Let's imagine we are programming a machine to mill a hole that is 20mm in diameter (which means a 10mm radius) and 5mm deep.

1. Inputs

  • Radius (R): 10 mm
    This defines the circular (rotary) part of the motion. The tool's center will follow a circular path with a 10mm radius.
  • Total Feed (V): 150 mm/minute
    Let's define this as the planar feed rate (the speed of the tool in the X-Y plane), which is a common way to program this.
  • Linear Component (Z-Plunge): 1 mm Pitch
    This is the linear part of the motion. We define this as a pitch—the vertical distance the tool will travel in one single revolution. This means to reach the full 5mm depth, the tool will need to complete 5 full revolutions.

2. Motion Analysis (Interpreting Fx, Fy)

Your terms Fx and Fy are best understood as the instantaneous velocity components of the tool's center in the X and Y axes. They are not constant inputs but rather the *result* of the circular motion.

The tool moves along the circular path (x, y) at a constant tangential speed of V = 150 mm/min. The position at any time can be described by an angle θ:

x = R cos(θ) = 10 cos(θ)
y = R sin(θ) = 10 sin(θ)

The velocity components (Fx and Fy) are the derivatives of this position. They are constantly changing:

Fx (or V_x) = -V sin(θ)
Fy (or V_y) = V cos(θ)

Example points:

  • At the "3 o'clock" position (θ = 0°): The tool moves purely "up."
    Fx = 0 mm/min, Fy = 150 mm/min
  • At the "12 o'clock" position (θ = 90°): The tool moves purely "left."
    Fx = -150 mm/min, Fy = 0 mm/min

The machine's controller calculates these changing Fx and Fy values automatically to maintain the constant circular feed V.

📊 Graphical Presentation

Here is a graphical breakdown of this combined motion.

Graphical interpretation of combined rotary and linear motion

3D (Isometric) View - "Combined Motion"

  • The path is a helix.
  • The Radius (R) is constant at 10 mm.
  • The Pitch (P) is 1 mm per loop.
  • The total motion consists of 5 loops to travel 5 mm deep.
Formulas:
Rotary only: F = V × (360 / (π × D))
Rotary + Linear: F = (180 / (π × R)) × √(V² − (Fx² + Fy²))

Calculator

All inputs must use the same linear unit

Set this to your rotary axis maximum angular speed. Default = 3600 °/min.

Rotary Feedrate
— °/min
Not calculated