Why is my actual chip thinner than the chip load I programmed?

Because the stepover is under half the tool diameter. Each tooth's arc of contact then stops short of where the chip is thickest. At 20% engagement the chip is 80% of feed per tooth.

Do I count flutes or inserts on an indexable cutter?

Count the inserts actually mounted: Mitsubishi Materials writes feed per tooth as table feed ÷ (inserts × RPM). An empty pocket takes no chip, so counting it understates chip load.

My catalog gives a chip load range. Which value do I enter?

Enter one end of the range, then run it again at the other. The two feeds to program bracket your starting window for that tool and material.

Will raising feed for chip thinning overload the spindle?

It can: spindle power rises in proportion to feed, so check it at the new feed. The Material Removal Rate calculator turns that feed into spindle horsepower for your material.

CNC Machining calculator

Chip Load Calculator

Check the chip each tooth really takes before you prove out a program or chase edge wear. You need feed, spindle speed, flutes, tool diameter, stepover and the catalog chip load.

What this calculator does

Chip load per tooth from feed, speed and flutes, corrected for radial chip thinning and checked against the catalog value.

Formula used

Chip load per tooth = feed rate ÷ (spindle speed × flutes)
Radial engagement = radial depth of cut ÷ tool diameter × 100
Thinning factor = 2 × √(radial depth × diameter − radial depth²) ÷ diameter below 50% engagement, otherwise 1
Actual chip = chip load per tooth × thinning factor; % of catalog = actual chip ÷ catalog chip load × 100
Chip load to program = catalog chip load ÷ thinning factor; feed to program = that × flutes × spindle speed

Inputs explained

Feed Rate: Programmed cutting feed from the CAM post or the control.
Spindle Speed: Programmed S value with any spindle override applied.
Flutes: Cutting edges on the end mill, or inserts on the cutter body.
Tool Diameter: Cutting diameter from the tool label or catalog.
Radial Depth of Cut: Stepover from the CAM toolpath, measured across the cutter.
Catalog Chip Load: Toolmaker's chart value (maximum chip thickness) for your material and diameter.

How to use the result

Best suited to proving out an adaptive roughing toolpath, finding why a finishing pass wears edges early.
Covers radial thinning only; ball nose and lead-angle cutters also thin the chip axially. Does not check surface speed, spindle power, deflection or chip evacuation.

Current U.S. benchmarks

The producer price index for steel mill products stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 17,154 machine shops establishments employing about 223,303 workers (Census County Business Patterns, 2023).

Common questions

Why is my actual chip thinner than the chip load I programmed? Because the stepover is under half the tool diameter. Each tooth's arc of contact then stops short of where the chip is thickest. At 20% engagement the chip is 80% of feed per tooth.
Do I count flutes or inserts on an indexable cutter? Count the inserts actually mounted: Mitsubishi Materials writes feed per tooth as table feed ÷ (inserts × RPM). An empty pocket takes no chip, so counting it understates chip load.
My catalog gives a chip load range. Which value do I enter? Enter one end of the range, then run it again at the other. The two feeds to program bracket your starting window for that tool and material.
Will raising feed for chip thinning overload the spindle? It can: spindle power rises in proportion to feed, so check it at the new feed. The Material Removal Rate calculator turns that feed into spindle horsepower for your material.

Related guides

Last reviewed 2026-10-01.