Tap Drill & Tapping Speed — UNC 3/8"-16 in Steel
Tap-drill size, RPM and synchronized feed for UNC 3/8"-16 in Steel (75%-thread rule with material-specific speed).
3/8"-16 in steel is the classic fixture-plate thread: drill letter "O" (8.0 mm) for ~72% engagement. Tap drill charts assume sharp drills — a worn drill cuts undersize and quietly raises engagement and torque.
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.
Tap-drill size, RPM and synchronized feed for UNC 3/8"-16 in Steel (75%-thread rule with material-specific speed). A free cnc machining: speeds, feeds & tool wear tool — no sign-up, no upload, instant results in your browser.
About Tap Drill & Tapping Speed — UNC 3/8"-16 in Steel
Tap Drill & Tapping Speed — UNC 3/8"-16 in Steel computes the governing relationship drill ≈ D − (P × %engagement / 76.98) · vf = n·P live as you type. 3/8"-16 in steel is the classic fixture-plate thread: drill letter "O" (8.0 mm) for ~72% engagement. Tap drill charts assume sharp drills — a worn drill cuts undersize and quietly raises engagement and torque. 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 Tap Drill & Tapping Speed — UNC 3/8"-16 in Steel
- 1Enter your values — Thread major diameter, Thread pitch, Tapping speed Vc, Thread engagement (sensible defaults are pre-filled).
- 2Read the live results: Tap drill diameter, Tapping RPM, Feed (locked to pitch).
- 3Check the "with your numbers" line to see drill ≈ D − (P × %engagement / 76.98) · vf = n·P substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Tap Drill & Tapping Speed — UNC 3/8"-16 in Steel?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula drill ≈ D − (P × %engagement / 76.98) · vf = n·P with authoritative sources cited on the page (Machinery's Handbook, 31st ed. — Speeds and Feeds; ISO 2306 — Drills for tapping holes)
- ✓3/8"-16 in steel is the classic fixture-plate thread: drill letter "O" (8.0 mm) for ~72% engagement.
- ✓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 tap drill & tapping speed — unc 3/8"-16 in steel use?+
It evaluates drill ≈ D − (P × %engagement / 76.98) · vf = n·P, exactly as published. Sources: Machinery's Handbook, 31st ed. — Speeds and Feeds; ISO 2306 — Drills for tapping holes. 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?+
3/8"-16 in steel is the classic fixture-plate thread: drill letter "O" (8.0 mm) for ~72% engagement. 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?+
Tap-drill size, RPM and synchronized feed for UNC 3/8"-16 in Steel (75%-thread rule with material-specific speed). A free cnc machining: speeds, feeds & tool wear tool. Tap drill charts assume sharp drills — a worn drill cuts undersize and quietly raises engagement and torque. 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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