Surface Finish Predictor — Boring Gray Cast Iron
Theoretical Ra and Rt from feed and nose radius for boring gray cast iron, checked against a Ra 3.2 target.
Bored iron surfaces show open graphite pores no feed reduction can close — Ra readings scatter accordingly. Spec'ing finer than Ra 1.6 on as-bored gray iron usually means you actually need honing.
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 boring gray cast iron, checked against a Ra 3.2 target. A free cnc machining: speeds, feeds & tool wear tool — no sign-up, no upload, instant results in your browser.
About Surface Finish Predictor — Boring Gray Cast Iron
Surface Finish Predictor — Boring Gray Cast Iron computes the governing relationship Ra ≈ f² / (32·rε) · Rt ≈ f² / (8·rε) live as you type. Bored iron surfaces show open graphite pores no feed reduction can close — Ra readings scatter accordingly. Spec'ing finer than Ra 1.6 on as-bored gray iron usually means you actually need honing. 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 — Boring Gray Cast Iron
- 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 — Boring Gray Cast Iron?
- ✓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)
- ✓Bored iron surfaces show open graphite pores no feed reduction can close — Ra readings scatter accordingly.
- ✓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 — boring gray cast iron 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?+
Bored iron surfaces show open graphite pores no feed reduction can close — Ra readings scatter accordingly. 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 boring gray cast iron, checked against a Ra 3.2 target. A free cnc machining: speeds, feeds & tool wear tool. Spec'ing finer than Ra 1.6 on as-bored gray iron usually means you actually need honing. 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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