Surface Finish Predictor — Facing to Center
Theoretical Ra and Rt from feed and nose radius for facing to center, checked against a Ra 1.6 target.
Facing finish degrades toward the center as surface speed falls to zero at constant RPM — use constant-surface-speed (G96) so the last millimetres look like the rim. The Ra model assumes speed stays adequate.
Formula
Note: Catalog starting values only — always confirm against your tool maker's data sheet and cut a test part. Machine rigidity, coolant and workholding shift real-world numbers.
Theoretical Ra and Rt from feed and nose radius for facing to center, checked against a Ra 1.6 target. A free cnc machining: speeds, feeds & tool wear tool — no sign-up, no upload, instant results in your browser.
About Surface Finish Predictor — Facing to Center
Surface Finish Predictor — Facing to Center computes the governing relationship Ra ≈ f² / (32·rε) · Rt ≈ f² / (8·rε) live as you type. Facing finish degrades toward the center as surface speed falls to zero at constant RPM — use constant-surface-speed (G96) so the last millimetres look like the rim. The Ra model assumes speed stays adequate. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Surface Finish Predictor — Facing to Center
- 1Enter your values — Feed per rev f, Nose radius rε, Target Ra (sensible defaults are pre-filled).
- 2Read the live results: Theoretical Ra, Theoretical Rt, Max feed for target.
- 3Check the "with your numbers" line to see Ra ≈ f² / (32·rε) · Rt ≈ f² / (8·rε) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Surface Finish Predictor — Facing to Center?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula Ra ≈ f² / (32·rε) · Rt ≈ f² / (8·rε) with authoritative sources cited on the page (Machinery's Handbook, 31st ed. — Speeds and Feeds; Sandvik Coromant — Milling formulas & definitions)
- ✓Facing finish degrades toward the center as surface speed falls to zero at constant RPM — use constant-surface-speed (G96) so the last millimetres look like the rim.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the surface finish predictor — facing to center use?+
It evaluates Ra ≈ f² / (32·rε) · Rt ≈ f² / (8·rε), exactly as published. Sources: Machinery's Handbook, 31st ed. — Speeds and Feeds; Sandvik Coromant — Milling formulas & definitions. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
Facing finish degrades toward the center as surface speed falls to zero at constant RPM — use constant-surface-speed (G96) so the last millimetres look like the rim. Catalog starting values only — always confirm against your tool maker's data sheet and cut a test part. Machine rigidity, coolant and workholding shift real-world numbers.
When is this calculator the right tool for the job?+
Theoretical Ra and Rt from feed and nose radius for facing to center, checked against a Ra 1.6 target. A free cnc machining: speeds, feeds & tool wear tool. The Ra model assumes speed stays adequate. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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