12.7 mm drill size
A 12.7 mm metric drill is 0.5000 in (12.700 mm). It is the cut tap, 50% thread drill for M14×2.0.
- Decimal inch
- 0.5000
- Millimeters
- 12.700
- Nearest 1/64
- 1/2" (+0.0000)
- Type
- metric drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 690 RPM and 0.0105 in/rev (7.25 IPM); in 6061 aluminum about 1,910 RPM.
12.7 mm drill speeds and feeds by material
Jobber-length twist drill, D = 0.5000 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 | 1,910 | 600 | 4,580 | 0.0100 | 19.1 | 45.8 |
| Brass / free-machining | 150 | 1,150 | 400 | 3,060 | 0.0083 | 9.55 | 25.4 |
| Low-carbon steel (1018) | 90 | 690 | 300 | 2,290 | 0.0105 | 7.25 | 24.1 |
| Alloy steel (4140, annealed) | 70 | 530 | 250 | 1,910 | 0.0115 | 6.10 | 22.0 |
| Stainless 304 | 40 | 310 | 150 | 1,150 | 0.0085 | 2.64 | 9.78 |
| Gray cast iron | 80 | 610 | 250 | 1,910 | 0.0085 | 5.19 | 16.2 |
| Titanium 6Al-4V | 25 | 190 | 100 | 760 | 0.0050 | 0.95 | 3.80 |
| Plastics (acetal) | 300 | 2,290 | 500 | 3,820 | 0.0060 | 13.7 | 22.9 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 690 RPM × 0.267 mm/rev = 184 mm/min.
Worked example: 12.7 mm drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.5000 ≈ 690 RPM.
- Feed for a 0.500 in drill in mild steel ≈ 0.0105 in/rev.
- IPM = 690 × 0.0105 = 7.25 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 1.500 in (38.1 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 2.500 in (63.5 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 4.000 in (101.6 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 12.7 mm drill
- M14×2.0 — cut tap, 50% thread · tap speeds and feeds
Nearest drills
- 1/2": 0.5000 in / 12.700 mm (0.0000 in)
- 12.6 mm: 0.4961 in / 12.600 mm (-0.0039 in)
- 12.8 mm: 0.5039 in / 12.800 mm (+0.0039 in)
- 12.5 mm: 0.4921 in / 12.500 mm (-0.0079 in)
Common questions
- What is a 12.7 mm drill in decimal and mm?
- 0.5000 in, or 12.700 mm; nearest fractional drill: 1/2" (0.5000 in, +0.0000 in); nearest number / letter drill: Letter Z (0.4130 in, -0.0870 in).
- What RPM for a 12.7 mm drill in steel?
- In low-carbon steel (1018) an HSS 12.7 mm drill (0.5000 in) runs about 690 RPM at 90 SFM; a carbide drill about 2,290 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a 12.7 mm drill?
- About 0.0105 in/rev in mild steel, 0.0100 in/rev in aluminum and 0.0085 in/rev in 304 stainless. At 690 RPM that is 7.25 IPM in steel (IPM = RPM × IPR).
- What RPM for a 12.7 mm drill in aluminum?
- 1,910 RPM with HSS (250 SFM) or up to 4,580 RPM with carbide (600 SFM), feeding about 0.0100 in/rev.
- What tap uses a 12.7 mm drill?
- M14×2.0 (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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