Below 50% radial engagement the maximum chip thickness is less than the programmed feed per tooth. Run the catalog fz anyway and the edge rubs, work-hardens the surface and dies early. This calculator gives the radial chip thinning factor and the adjusted feed per tooth, with optional lead-angle compensation. Runs entirely in your browser.
At ae ≥ 50% of D there is no radial thinning: run the recommended fz as programmed. Feed adjustments raise chip load per tooth deliberately — check spindle torque and workholding before applying large factors.
The maximum chip thickness in milling is the feed per tooth times the sine of the maximum engagement angle. With a full half-immersion or more, that angle reaches 90° and hex equals fz. At light radial engagement the cutter exits the cut before the chip reaches full thickness:
A carbide edge needs a minimum chip thickness to cut instead of plough. At 10% stepover the thinning factor is about 1.67: programmed at catalog fz, your real chip is 40% thinner than the maker intended, the edge rubs, and tool life collapses while everything looks fine on paper. Compensating the feed restores the chip the grade was designed for and usually raises productivity at the same time.
Whenever the radial stepover is below half the cutter diameter, which covers most HSM, peel-milling and finishing toolpaths. The lighter the engagement, the bigger the correction: at 20% ae the factor is about 1.25, at 10% about 1.67, at 5% about 2.29.
Yes, independently of the radial effect. A 45° face mill produces a chip about 71% as thick as the programmed feed (sin 45°), and round inserts thin it further at shallow depths. Divide the feed by sin κr to compensate; this calculator combines both effects.
The chip does not object; the rest of the setup might. Large factors raise the load on the tool, the spindle and the fixture, and long slender cutters can deflect. Apply the factor, then work up to it in steps if the machine or the part is marginal.
Use the feed per tooth your insert or cutter maker recommends for the grade and material: that value IS the intended maximum chip thickness at full engagement. This calculator scales your programmed feed so the real chip matches it at light engagement. For a grounded per-tool recommendation, ask the advisor.
This page corrects the feed you already chose. Which grade and starting fz for your material and cutter is the advisor's job, grounded in catalog data across 13 brands, brand-neutral.