Chip Chad

Chip Load Calculator

Most people running a hobby CNC never calculate chip load. They pick a feed rate that sounds safe, listen for chatter, watch the chips, and call it good. This works — until it costs them a $25 end mill that should have lasted a hundred parts, or a surface finish that needed three passes to clean up. Chip load is the number behind most unexplained tool failures.

What chip load actually is

Chip load is the thickness of the material each cutting edge removes per revolution — the real work each flute does. Feed rate divided by RPM divided by flute count. Too low and the tool rubs instead of cuts: heat builds in the edge instead of leaving with the chip, which work-hardens steel, glazes aluminum, and accelerates wear faster than actually cutting would. Too high and the edge overloads: deflection, chatter, or a snapped tool. The goal is a chip thick enough to carry heat away from the edge and thin enough not to overload it.

  • Too low: rubbing, heat in the tool, short tool life and poor finish.
  • Too high: overload, deflection, chatter, breakage.
  • Correct: chip carries heat away, edge stays cool, tool life is predictable.

Why the math changes when you swap tools or tighten your stepover

Feed rate is chip load multiplied by flute count multiplied by RPM. Swap a 2-flute for a 4-flute at the same feed rate and you have halved the chip load per tooth — pushing a sticky aluminum alloy straight into the rubbing zone without changing a single number in your CAM. Tighten your stepover for a better surface finish and the same thing happens: at low radial engagement, the actual chip thickness drops below the nominal chip load due to radial chip thinning. Feed rate needs to go up to compensate, or the tool is rubbing on a finishing pass. Chip Chad accounts for both automatically.

  • More flutes at the same feed rate means less chip load per tooth.
  • Low stepover reduces effective chip thickness — feed harder, not softer, for finishes.
  • Chip Chad compensates for flute count and radial chip thinning in every recommendation.