DFM Corner Ratio

Design for Manufacturability (DFM): Calculate the required Tool Length-to-Diameter (L:D) ratio to evaluate how difficult and expensive a pocket will be to machine.

If enabled, assumes the tool diameter will be 20% smaller than the corner size to allow the machine to sweep the corner without chattering.
Manufacturability Score
Required L:D Ratio
0.0
: 1
--
0
3
5
8
10+
Max Tool Diameter
0.000 in
Ideal Radius (For 3:1)
0.000 in
The Physics of Deflection
Depth R

An end mill acts as a cantilever beam. Tool deflection (bending) increases by the cube of the length. A tool sticking out twice as far will deflect 8 times as much under the same cutting force.

L:D Ratio Guidelines
  • < 3:1 (Green): Optimal. Standard tool lengths. High material removal rates, low cost, excellent surface finish.
  • 3:1 to 5:1 (Blue): Standard. Requires slightly reduced feeds/speeds but uses readily available tooling.
  • 5:1 to 8:1 (Yellow): Difficult. Requires carbide tooling with relieved shanks. Multiple light spring passes needed to eliminate taper. Costs increase 2-3x.
  • > 8:1 (Red): Extreme. Custom heavy-metal/carbide vibration-dampened tooling required. Slow, very expensive. Often requires EDM or redesign.
DFM Tip: Never design a pocket corner radius to be the exact radius of a standard end mill. The tool will "wrap" the corner, engaging 90° of the cutter at once, causing massive chatter. Always oversize the corner radius by at least 20% to allow for circular interpolation.