9.4 mm drill size
A 9.4 mm metric drill is 0.3701 in (9.400 mm). It is the form (roll) tap, 65% thread drill for M10x1.25.
- Decimal inch
- 0.3701
- Millimeters
- 9.400
- Nearest 1/64
- 3/8" (-0.0049)
- Type
- metric drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 930 RPM and 0.0094 in/rev (8.74 IPM); in 6061 aluminum about 2,580 RPM.
9.4 mm drill speeds and feeds by material
Jobber-length twist drill, D = 0.3701 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 | 2,580 | 600 | 6,190 | 0.0084 | 21.7 | 52.0 |
| Brass / free-machining | 150 | 1,550 | 400 | 4,130 | 0.0062 | 9.61 | 25.6 |
| Low-carbon steel (1018) | 90 | 930 | 300 | 3,100 | 0.0094 | 8.74 | 29.1 |
| Alloy steel (4140, annealed) | 70 | 720 | 250 | 2,580 | 0.0103 | 7.42 | 26.6 |
| Stainless 304 | 40 | 410 | 150 | 1,550 | 0.0062 | 2.54 | 9.61 |
| Gray cast iron | 80 | 830 | 250 | 2,580 | 0.0064 | 5.31 | 16.5 |
| Titanium 6Al-4V | 25 | 260 | 100 | 1,030 | 0.0042 | 1.09 | 4.33 |
| Plastics (acetal) | 300 | 3,100 | 500 | 5,160 | 0.0050 | 15.5 | 25.8 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 930 RPM × 0.239 mm/rev = 222 mm/min.
Worked example: 9.4 mm drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.3701 ≈ 930 RPM.
- Feed for a 0.370 in drill in mild steel ≈ 0.0094 in/rev.
- IPM = 930 × 0.0094 = 8.74 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 1.110 in (28.2 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 1.850 in (47 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 2.961 in (75.2 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 9.4 mm drill
Nearest drills
- Letter U: 0.3680 in / 9.347 mm (-0.0021 in)
- 9.3 mm: 0.3661 in / 9.300 mm (-0.0039 in)
- 9.5 mm: 0.3740 in / 9.500 mm (+0.0039 in)
- 3/8": 0.3750 in / 9.525 mm (+0.0049 in)
Common questions
- What is a 9.4 mm drill in decimal and mm?
- 0.3701 in, or 9.400 mm; nearest fractional drill: 3/8" (0.3750 in, +0.0049 in); nearest number / letter drill: Letter U (0.3680 in, -0.0021 in).
- What RPM for a 9.4 mm drill in steel?
- In low-carbon steel (1018) an HSS 9.4 mm drill (0.3701 in) runs about 930 RPM at 90 SFM; a carbide drill about 3,100 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a 9.4 mm drill?
- About 0.0094 in/rev in mild steel, 0.0084 in/rev in aluminum and 0.0062 in/rev in 304 stainless. At 930 RPM that is 8.74 IPM in steel (IPM = RPM × IPR).
- What RPM for a 9.4 mm drill in aluminum?
- 2,580 RPM with HSS (250 SFM) or up to 6,190 RPM with carbide (600 SFM), feeding about 0.0084 in/rev.
- What tap uses a 9.4 mm drill?
- M10x1.25 (form (roll) tap, 65% thread); M10x1 (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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