Trochoidal- & HSM-Vorschubrechner
With radial engagement below half the tool diameter, the actual chip becomes thinner than your set feed per tooth. This calculator determines the necessary correction factor so you can utilise the full potential of trochoidal and HSM strategies.
Hinweis: All values are non-binding reference figures. Actual values depend on machine, tool, material and Bedingungen ab. Beginnen Sie konservativ. Eine Haftung für Werkzeugbruch, Maschinenschäden oder Bearbeitungsergebnisse wird nicht übernommen.
What the Chip Thinning Calculator Computes
When trochoidal and HSM milling, you deliberately work with a small radial depth of cut (ae). As soon as ae is smaller than half the tool diameter (d/2), the tooth only engages over a short arc. The actual maximum chip thickness therefore falls below the set feed per tooth (fz). The cutting edge rubs more than it cuts, tool life suffers, and the material removal rate remains underutilised. The calculator determines the correction factor from diameter and radial depth of cut and outputs the feed rate to be increased directly.
The Formula for Chip Thickness Correction
The Radial Chip Thinning Factor (RCTF) is calculated from tool diameter d and radial depth of cut ae:
RCTF = d / (2 × √(ae × (d − ae)))
The corrected feed per tooth is then derived as:
fz, corrected = fz × RCTF
For orientation, some typical values:
| Radial depth of cut ae | Correction factor (RCTF) |
|---|---|
| 50 % of d (ae = d/2) | 1.0 |
| 25 % of d | 1.15 |
| 10 % of d | 1.67 |
At ae = d/2 the factor is exactly 1.0 — here the chip thickness corresponds to the set fz, and no correction is necessary. The smaller the radial depth of cut, the greater the increase.
How to Apply the Result
- Enter the tool diameter, planned radial depth of cut, and your base fz from the manufacturer's data sheet.
- Transfer the corrected feed per tooth into your CAM system.
- The corrected chip thickness remains at the value specified by the tool manufacturer — so you do not exceed the cutting edge's load limit.
What You Should Watch Out For
The feed rate increase requires a rigid machine and spindle, as the higher table speed demands contour accuracy and dynamics. Chip thickness correction is the computational basis of trochoidal and HSM milling and only delivers its full benefit in combination with a suitable toolpath strategy, adequate cooling, and stable tool holding.
Further calculations can be found in our overview of CNC calculators. Background on strategies and cutting parameters is available in the BZT Knowledge Centre.
Frequently Asked Questions
What is chip thinning (chip thickness correction)?
When the radial depth of cut ae is below d/2, the tooth only engages over a short arc, so the actual chip thickness falls below the set feed per tooth. To achieve the intended chip thickness, fz is multiplied by the correction factor.
What is the formula for the correction factor?
The Radial Chip Thinning Factor is RCTF = d / (2 × √(ae × (d − ae))). The corrected feed is derived from fz, corrected = fz × RCTF.
From which depth of cut do I need to correct?
Only when the radial depth of cut falls below d/2 (50 % of the diameter) does the chip become thinner than fz. Exactly at ae = d/2 the factor is 1.0, at 25 % approximately 1.15, and at 10 % about 1.67.
Are there prerequisites for increasing the feed rate?
Yes. The correction requires a rigid machine and spindle and forms the computational basis of trochoidal and HSM milling. It only works in combination with a suitable toolpath strategy and stable tool holding.
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