#30 drill size
A #30 number (wire-gauge) drill is 0.1285 in (3.264 mm). It is the form (roll) tap, 65% thread drill for 6-40.
- Decimal inch
- 0.1285
- Millimeters
- 3.264
- Nearest 1/64
- 1/8" (+0.0035)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 2,680 RPM and 0.0030 in/rev (8.04 IPM); in 6061 aluminum about 7,430 RPM.
#30 drill speeds and feeds by material
Jobber-length twist drill, D = 0.1285 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.
| Material | HSS SFM | HSS RPM | Carbide SFM | Carbide RPM | Feed (in/rev) | HSS IPM | Carbide IPM |
|---|---|---|---|---|---|---|---|
| Aluminum (6061) | 250 | 7,430 | 600 | 17,840 | 0.0029 | 21.6 | 51.7 |
| Brass / free-machining | 150 | 4,460 | 400 | 11,890 | 0.0025 | 11.2 | 29.7 |
| Low-carbon steel (1018) | 90 | 2,680 | 300 | 8,920 | 0.0030 | 8.04 | 26.8 |
| Alloy steel (4140, annealed) | 70 | 2,080 | 250 | 7,430 | 0.0030 | 6.24 | 22.3 |
| Stainless 304 | 40 | 1,190 | 150 | 4,460 | 0.0021 | 2.50 | 9.37 |
| Gray cast iron | 80 | 2,380 | 250 | 7,430 | 0.0019 | 4.52 | 14.1 |
| Titanium 6Al-4V | 25 | 740 | 100 | 2,970 | 0.0016 | 1.18 | 4.75 |
| Plastics (acetal) | 300 | 8,920 | 500 | 14,860 | 0.0050 | 44.6 | 74.3 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,680 RPM × 0.076 mm/rev = 204 mm/min.
Worked example: #30 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.1285 ≈ 2,680 RPM.
- Feed for a 0.129 in drill in mild steel ≈ 0.0030 in/rev.
- IPM = 2,680 × 0.0030 = 8.04 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.386 in (9.8 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.643 in (16.3 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.028 in (26.1 mm) | G83 full retract | 0.5-1 × D, shrinking with depth | Retract to clear chips; reduce feed ~10-20% past 5×D. |
Taps that use a #30 drill
- 6-40 — form (roll) tap, 65% thread · tap speeds and feeds
Nearest drills
- 3.3 mm: 0.1299 in / 3.300 mm (+0.0014 in)
- 3.2 mm: 0.1260 in / 3.200 mm (-0.0025 in)
- 1/8": 0.1250 in / 3.175 mm (-0.0035 in)
- 3.4 mm: 0.1339 in / 3.400 mm (+0.0054 in)
Common questions
- What is a #30 drill in decimal and mm?
- 0.1285 in, or 3.264 mm; nearest fractional drill: 1/8" (0.1250 in, -0.0035 in); nearest metric drill: 3.3 mm (0.1299 in, +0.0014 in).
- What RPM for a #30 drill in steel?
- In low-carbon steel (1018) an HSS #30 drill (0.1285 in) runs about 2,680 RPM at 90 SFM; a carbide drill about 8,920 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #30 drill?
- About 0.0030 in/rev in mild steel, 0.0029 in/rev in aluminum and 0.0021 in/rev in 304 stainless. At 2,680 RPM that is 8.04 IPM in steel (IPM = RPM × IPR).
- What RPM for a #30 drill in aluminum?
- 7,430 RPM with HSS (250 SFM) or up to 17,840 RPM with carbide (600 SFM), feeding about 0.0029 in/rev.
- What tap uses a #30 drill?
- 6-40 (form (roll) tap, 65% thread).
Nearby drill sizes
Sources
- Machinery's Handbook, 31st ed., Speeds and Feeds for Drilling, Reaming and Threading (Tables 17-23) — HSS and carbide drilling SFM (rounded).
- RedLine Tools (Productivity Inc.) catalog p. 340, Cobalt & HSS Drills Speeds & Feeds — feed per rev by drill diameter and material (middle of the catalog range).
- ASME B94.11M twist drills: number (#1-#80) and letter (A-Z) drill sizes; drill size reference.
Material feed multipliers (aluminum 1.3×, brass 1.1×, 4140 0.85×, stainless and titanium 0.7× the mild-steel feed) are JobLine estimates. Peck guidance is JobLine shop practice. Use your drill maker's data first.
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