A hole that merely exceeds the nominal screw diameter may not assemble reliably once positional error, burrs, coatings and process variation are included.
Documented clearance recommendations
These values reproduce the cited manufacturer recommendations, not protected standard tables. A blank cell means that fit category is not supplied by this dataset.
| Fastener | Close | General | Free |
|---|---|---|---|
| #4 | #32 · 0.1160 in | — | #30 · 0.1285 in |
| #6 | #27 · 0.1440 in | — | #25 · 0.1495 in |
| #8 | #18 · 0.1695 in | — | #16 · 0.1770 in |
| #10 | #9 · 0.1960 in | — | #7 · 0.2010 in |
| 1/4 in | F · 0.2570 in | — | H · 0.2660 in |
| 5/16 in | P · 0.3230 in | — | Q · 0.3320 in |
| 3/8 in | W · 0.3860 in | — | X · 0.3970 in |
| 7/16 in | 29/64 in · 0.453125 in | — | 15/32 in · 0.46875 in |
| 1/2 in | 33/64 in · 0.515625 in | — | 17/32 in · 0.53125 in |
| 5/8 in | 41/64 in · 0.640625 in | — | 21/32 in · 0.65625 in |
| 3/4 in | 49/64 in · 0.765625 in | — | 25/32 in · 0.78125 in |
| 7/8 in | 57/64 in · 0.890625 in | — | 29/32 in · 0.90625 in |
| 1 in | 1-1/64 in · 1.015625 in | — | 1-1/32 in · 1.03125 in |
What the fit labels mean
Close minimizes extra movement but demands good alignment and process control. General provides more ordinary assembly margin. Free provides additional room where alignment or rapid assembly matters more than location.
- Start from the actual fastener diameter/callout.
- Account for plating, paint and burrs.
- Use the drawing or licensed standard when it specifies a hole.
Why a fixed allowance is limited
Formal clearance-hole series are size-dependent and interact with positional tolerances. The calculator’s fixed diametric increments make the arithmetic visible but do not reproduce a standard table.
Do not use these allowances for structural, aerospace, pressure-boundary or safety-critical design without engineering control.
Technical references
- Cle-Line C01112 Tap and Drill Recommendations — Greenfield Industries / Cle-Line. Accessed 2026-11-09.
- Decimal Equivalent & Drill Size Chart — Travers Tool Co.. Accessed 2026-11-09.
- ASME B1.1-2024 Unified Inch Screw Threads — ASME. Accessed 2026-11-10.
Standards references identify scope and terminology; protected dimensional tables are not reproduced.