12.5 mm drill size
A 12.5 mm metric drill is 0.4921 in (12.500 mm). It is the cut tap, 75% thread drill for M14x1.5.
- Decimal inch
- 0.4921
- Millimeters
- 12.500
- Nearest 1/64
- 31/64" (+0.0078)
- Type
- metric drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 700 RPM and 0.0104 in/rev (7.28 IPM); in 6061 aluminum about 1,940 RPM.
12.5 mm drill speeds and feeds by material
Jobber-length twist drill, D = 0.4921 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 | 1,940 | 600 | 4,660 | 0.0099 | 19.2 | 46.1 |
| Brass / free-machining | 150 | 1,160 | 400 | 3,100 | 0.0081 | 9.40 | 25.1 |
| Low-carbon steel (1018) | 90 | 700 | 300 | 2,330 | 0.0104 | 7.28 | 24.2 |
| Alloy steel (4140, annealed) | 70 | 540 | 250 | 1,940 | 0.0114 | 6.16 | 22.1 |
| Stainless 304 | 40 | 310 | 150 | 1,160 | 0.0084 | 2.60 | 9.74 |
| Gray cast iron | 80 | 620 | 250 | 1,940 | 0.0084 | 5.21 | 16.3 |
| Titanium 6Al-4V | 25 | 190 | 100 | 780 | 0.0050 | 0.95 | 3.90 |
| Plastics (acetal) | 300 | 2,330 | 500 | 3,880 | 0.0059 | 13.8 | 22.9 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 700 RPM × 0.264 mm/rev = 185 mm/min.
Worked example: 12.5 mm drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.4921 ≈ 700 RPM.
- Feed for a 0.492 in drill in mild steel ≈ 0.0104 in/rev.
- IPM = 700 × 0.0104 = 7.28 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 1.476 in (37.5 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 2.461 in (62.5 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 3.937 in (100 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 12.5 mm drill
- M14x1.5 — cut tap, 75% thread
Nearest drills
- 12.6 mm: 0.4961 in / 12.600 mm (+0.0039 in)
- 12.4 mm: 0.4882 in / 12.400 mm (-0.0039 in)
- 31/64": 0.4844 in / 12.303 mm (-0.0078 in)
- 1/2": 0.5000 in / 12.700 mm (+0.0079 in)
Common questions
- What is a 12.5 mm drill in decimal and mm?
- 0.4921 in, or 12.500 mm; nearest fractional drill: 31/64" (0.4844 in, -0.0078 in); nearest number / letter drill: Letter Z (0.4130 in, -0.0791 in).
- What RPM for a 12.5 mm drill in steel?
- In low-carbon steel (1018) an HSS 12.5 mm drill (0.4921 in) runs about 700 RPM at 90 SFM; a carbide drill about 2,330 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a 12.5 mm drill?
- About 0.0104 in/rev in mild steel, 0.0099 in/rev in aluminum and 0.0084 in/rev in 304 stainless. At 700 RPM that is 7.28 IPM in steel (IPM = RPM × IPR).
- What RPM for a 12.5 mm drill in aluminum?
- 1,940 RPM with HSS (250 SFM) or up to 4,660 RPM with carbide (600 SFM), feeding about 0.0099 in/rev.
- What tap uses a 12.5 mm drill?
- M14x1.5 (cut tap, 75% 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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