Tool nose radius compensation

If you program a chamfer or taper with the tool offset set on the imaginary tip and no G41/G42, the nose radius leaves extra material on the angle. This works out how far to move the line.

Example code – check it and dry-run it, at your own risk. This program is a generic example, not written for your machine or control. Read every line against your control’s manual, simulate it, then run it above the work in single block with reduced rapids and feed before cutting. Check the work offset, tool length offset, units and clearance heights. See the terms of use.

How it works, guides and notes

How it works

The imaginary tip is the corner where the two tangent lines of the nose meet. Running that point along an angled line leaves the round nose short of the line by r(sin θ + cos θ − 1) at right angles to it. Dividing by sin θ gives the shift along Z, r(1 − tan(θ/2)), and dividing by cos θ gives the radial shift, r(1 − tan((90° − θ)/2)). Double the radial figure for a diameter-programmed lathe.

Hand check: 45° chamfer, 0.8 mm nose: shift = 0.8 × (1 − tan 22.5°) = 0.8 × 0.585786 = 0.4686 mm in Z, or 0.9373 mm on diameter.

Move the line into the material, then check the first part. With G41/G42 and the right tip direction, the control does this itself. See the G-code reference.

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