#12 drill size
A #12 number (wire-gauge) drill is 0.1890 in (4.801 mm). It is the cut tap, 50% thread drill for 12-24.
- Decimal inch
- 0.1890
- Millimeters
- 4.801
- Nearest 1/64
- 3/16" (+0.0015)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 1,820 RPM and 0.0048 in/rev (8.74 IPM); in 6061 aluminum about 5,050 RPM.
#12 drill speeds and feeds by material
Jobber-length twist drill, D = 0.1890 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 | 5,050 | 600 | 12,130 | 0.0045 | 22.7 | 54.6 |
| Brass / free-machining | 150 | 3,030 | 400 | 8,080 | 0.0039 | 11.8 | 31.5 |
| Low-carbon steel (1018) | 90 | 1,820 | 300 | 6,060 | 0.0048 | 8.74 | 29.1 |
| Alloy steel (4140, annealed) | 70 | 1,410 | 250 | 5,050 | 0.0048 | 6.77 | 24.2 |
| Stainless 304 | 40 | 810 | 150 | 3,030 | 0.0032 | 2.59 | 9.70 |
| Gray cast iron | 80 | 1,620 | 250 | 5,050 | 0.0032 | 5.18 | 16.2 |
| Titanium 6Al-4V | 25 | 510 | 100 | 2,020 | 0.0023 | 1.17 | 4.65 |
| Plastics (acetal) | 300 | 6,060 | 500 | 10,110 | 0.0045 | 27.3 | 45.5 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,820 RPM × 0.122 mm/rev = 222 mm/min.
Worked example: #12 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.1890 ≈ 1,820 RPM.
- Feed for a 0.189 in drill in mild steel ≈ 0.0048 in/rev.
- IPM = 1,820 × 0.0048 = 8.74 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.567 in (14.4 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.945 in (24 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.512 in (38.4 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 #12 drill
- 12-24 — cut tap, 50% thread · tap speeds and feeds
Nearest drills
- 4.8 mm: 0.1890 in / 4.800 mm (-0.0000 in)
- 3/16": 0.1875 in / 4.762 mm (-0.0015 in)
- #11: 0.1910 in / 4.851 mm (+0.0020 in)
- 4.9 mm: 0.1929 in / 4.900 mm (+0.0039 in)
Common questions
- What is a #12 drill in decimal and mm?
- 0.1890 in, or 4.801 mm; nearest fractional drill: 3/16" (0.1875 in, -0.0015 in); nearest metric drill: 4.8 mm (0.1890 in, -0.0000 in).
- What RPM for a #12 drill in steel?
- In low-carbon steel (1018) an HSS #12 drill (0.1890 in) runs about 1,820 RPM at 90 SFM; a carbide drill about 6,060 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #12 drill?
- About 0.0048 in/rev in mild steel, 0.0045 in/rev in aluminum and 0.0032 in/rev in 304 stainless. At 1,820 RPM that is 8.74 IPM in steel (IPM = RPM × IPR).
- What RPM for a #12 drill in aluminum?
- 5,050 RPM with HSS (250 SFM) or up to 12,130 RPM with carbide (600 SFM), feeding about 0.0045 in/rev.
- What tap uses a #12 drill?
- 12-24 (cut tap, 50% 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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