Facing Time (Constant Surface Speed)
Facing time from bar diameter, feed and constant surface speed (G96), where RPM rises toward center.
G96 facing time is not linear in radius: the outer rings pass quickly while the capped center crawls. The RPM cap output shows where your machine stops being speed-limited — a bigger cap shortens facing more than more feed does.
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.
Facing time from bar diameter, feed and constant surface speed (G96), where RPM rises toward center. A free cnc machining: speeds, feeds & tool wear tool — no sign-up, no upload, instant results in your browser.
About Facing Time (Constant Surface Speed)
Facing Time (Constant Surface Speed) computes the governing relationship t = π(R²−r²)/(Vc·f) + r/(n_max·f) live as you type. G96 facing time is not linear in radius: the outer rings pass quickly while the capped center crawls. The RPM cap output shows where your machine stops being speed-limited — a bigger cap shortens facing more than more feed does. 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 Facing Time (Constant Surface Speed)
- 1Enter your values — Bar diameter, Surface speed Vc, Feed per rev, Spindle RPM cap (sensible defaults are pre-filled).
- 2Read the live results: Facing time, Radius where RPM caps.
- 3Check the "with your numbers" line to see t = π(R²−r²)/(Vc·f) + r/(n_max·f) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Facing Time (Constant Surface Speed)?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula t = π(R²−r²)/(Vc·f) + r/(n_max·f) with authoritative sources cited on the page (Machinery's Handbook, 31st ed. — Speeds and Feeds; Kalpakjian & Schmid, Manufacturing Engineering and Technology, 7th ed., ch. 21)
- ✓G96 facing time is not linear in radius: the outer rings pass quickly while the capped center crawls.
- ✓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 facing time (constant surface speed) use?+
It evaluates t = π(R²−r²)/(Vc·f) + r/(n_max·f), exactly as published. Sources: Machinery's Handbook, 31st ed. — Speeds and Feeds; Kalpakjian & Schmid, Manufacturing Engineering and Technology, 7th ed., ch. 21. 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?+
G96 facing time is not linear in radius: the outer rings pass quickly while the capped center crawls. 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?+
Facing time from bar diameter, feed and constant surface speed (G96), where RPM rises toward center. A free cnc machining: speeds, feeds & tool wear tool. The RPM cap output shows where your machine stops being speed-limited — a bigger cap shortens facing more than more feed does. 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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