#6-32
- Conditional drill estimate
- 2.783 mm
- D − pitch estimate
- 2.711 mm
- Series
- UNC
VALICALC · TECHNICAL REFERENCE
UNC / UNF Tap Drill Chart
Choose a US thread designation to look up its starting cutting-tap drill. Compare drill equivalents while keeping the thread series and tapping process visible.
QUICK LOOKUP
Search within the verified subset. Numeric sizes match complete designations; a nearby size is a candidate, not an exact match.
SELECTED REFERENCE
1/4-20
- Conditional drill estimate
- 5.195 mm
- D − pitch estimate
- 5.08 mm
- Series
- UNC
All fields & cell provenance
- Cutting tap: OSG Tap Drill Size chart — Cutting-tap equation and nominal size / 1/4-20 · verified 2026-10-06 · source value 1/4-20.
- Conditional drill estimate: OSG Tap Drill Size chart — Cutting-tap equation and nominal size / 1/4-20 · verified 2026-10-06.
- D − pitch estimate: OSG Tap Drill Size chart — Cutting-tap equation and nominal size / 1/4-20 · verified 2026-10-06.
- Series: Bolt Depot US thread pitch product reference — US TPI series / 1/4-20 · verified 2026-10-06 · source value UNC.
v1.1.0 · verified 2026-10-06 · values use the valid conditions shown above
1/4-205.195 mmBack to answer ↑
Explore the verified data
16 matching rows · 16 in this subset
| Cutting tap | Conditional drill estimate | D − pitch estimate | Series | Actions |
|---|---|---|---|---|
| #6-32 | 2.783 mm | 2.711 mm | UNC | |
| #6-40 | 2.928 mm | 2.87 mm | UNF | |
| #8-32 | 3.444 mm | 3.372 mm | UNC | |
| #8-36 | 3.524 mm | 3.46 mm | UNF | |
| #10-24 | 3.864 mm | 3.768 mm | UNC | |
| #10-32 | 4.104 mm | 4.032 mm | UNF | |
| 1/4-20 | 5.195 mm | 5.08 mm | UNC | |
| 1/4-28 | 5.525 mm | 5.443 mm | UNF | |
| 5/16-18 | 6.654 mm | 6.526 mm | UNC | |
| 5/16-24 | 6.975 mm | 6.879 mm | UNF | |
| 3/8-16 | 8.081 mm | 7.938 mm | UNC | |
| 3/8-24 | 8.563 mm | 8.467 mm | UNF | |
| 1/2-13 | 10.923 mm | 10.746 mm | UNC | |
| 1/2-20 | 11.545 mm | 11.43 mm | UNF | |
| 3/4-10 | 16.74 mm | 16.51 mm | UNC | |
| 3/4-16 | 17.606 mm | 17.463 mm | UNF |
#6-40
- Conditional drill estimate
- 2.928 mm
- D − pitch estimate
- 2.87 mm
- Series
- UNF
#8-32
- Conditional drill estimate
- 3.444 mm
- D − pitch estimate
- 3.372 mm
- Series
- UNC
#8-36
- Conditional drill estimate
- 3.524 mm
- D − pitch estimate
- 3.46 mm
- Series
- UNF
#10-24
- Conditional drill estimate
- 3.864 mm
- D − pitch estimate
- 3.768 mm
- Series
- UNC
#10-32
- Conditional drill estimate
- 4.104 mm
- D − pitch estimate
- 4.032 mm
- Series
- UNF
1/4-20
- Conditional drill estimate
- 5.195 mm
- D − pitch estimate
- 5.08 mm
- Series
- UNC
1/4-28
- Conditional drill estimate
- 5.525 mm
- D − pitch estimate
- 5.443 mm
- Series
- UNF
5/16-18
- Conditional drill estimate
- 6.654 mm
- D − pitch estimate
- 6.526 mm
- Series
- UNC
5/16-24
- Conditional drill estimate
- 6.975 mm
- D − pitch estimate
- 6.879 mm
- Series
- UNF
3/8-16
- Conditional drill estimate
- 8.081 mm
- D − pitch estimate
- 7.938 mm
- Series
- UNC
3/8-24
- Conditional drill estimate
- 8.563 mm
- D − pitch estimate
- 8.467 mm
- Series
- UNF
1/2-13
- Conditional drill estimate
- 10.923 mm
- D − pitch estimate
- 10.746 mm
- Series
- UNC
1/2-20
- Conditional drill estimate
- 11.545 mm
- D − pitch estimate
- 11.43 mm
- Series
- UNF
3/4-10
- Conditional drill estimate
- 16.74 mm
- D − pitch estimate
- 16.51 mm
- Series
- UNC
3/4-16
- Conditional drill estimate
- 17.606 mm
- D − pitch estimate
- 17.463 mm
- Series
- UNF
How to use this data
D −0.01299×percentage/TPI in inches, converted exactly to millimetres; D-P shown separately. Source method is OSG's cutting-tap equation, not its paid-standard limits.
- Full-thread percentage is explicit and editable. Cut taps only.
- Compare smaller/larger stock drills in the Drill Bit Size lookup before selecting a drill.
CHECK THE METHOD
Worked example
1/4-20 at 70%: estimate 0.204535 in (5.195189 mm); at 75%: 0.2012875 in. The common#7 drill is 0.2010 in, a distinct stock size.
Continue the reference workflow
Common lookup questions
Why is#7 not always the 1/4-20 answer?
It is a common stock drill near one percentage scenario. Different engagement, materials and tolerance requirements can need a different starting hole.
TRACEABLE DATA
Sources, scope & verification
Dataset v1.1.0
Last verified:
16 common UNC/UNF cutting-tap scenarios. Generated percentage-based values are not supplier drill recommendations.
Values are curated product facts or generated scenarios. Paid standards, complete catalogs and source diagrams are not reproduced. A verification date applies to this documented subset.
OSG Tap Drill Size chart ↗
Type A · OSG · 800274CA-V3 / 2024
Original equations and generated scenario values; no copied reference table.
Full provenance & artifact record
- Source checked
- 2026-10-06
- Use basis
- authored-formula
- Artifact SHA-256
- 20cf70a1a4b075ed05a818f08b16f1bed2161219258d8752e41d149489f05a51
Bolt Depot US thread pitch product reference ↗
Type C · BOLT · page version not stated
Selected dimensional product facts only; no catalog text, diagrams, standard tolerances or full paid-standard tables.
Full provenance & artifact record
- Source checked
- 2026-10-06
- Use basis
- bounded-product-facts
- Artifact SHA-256
- Public web page inspected; no retained source artifact hash.