3.8 mm drill size
A 3.8 mm metric drill is 0.1496 in (3.800 mm). It is the form (roll) tap, 65% thread drill for M4x0.5.
- Decimal inch
- 0.1496
- Millimeters
- 3.800
- Nearest 1/64
- 5/32" (-0.0066)
- Type
- metric drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 2,300 RPM and 0.0036 in/rev (8.28 IPM); in 6061 aluminum about 6,380 RPM.
3.8 mm drill speeds and feeds by material
Jobber-length twist drill, D = 0.1496 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 | 6,380 | 600 | 15,320 | 0.0035 | 22.3 | 53.6 |
| Brass / free-machining | 150 | 3,830 | 400 | 10,210 | 0.0030 | 11.5 | 30.6 |
| Low-carbon steel (1018) | 90 | 2,300 | 300 | 7,660 | 0.0036 | 8.28 | 27.6 |
| Alloy steel (4140, annealed) | 70 | 1,790 | 250 | 6,380 | 0.0036 | 6.44 | 23.0 |
| Stainless 304 | 40 | 1,020 | 150 | 3,830 | 0.0024 | 2.45 | 9.19 |
| Gray cast iron | 80 | 2,040 | 250 | 6,380 | 0.0023 | 4.69 | 14.7 |
| Titanium 6Al-4V | 25 | 640 | 100 | 2,550 | 0.0018 | 1.15 | 4.59 |
| Plastics (acetal) | 300 | 7,660 | 500 | 12,770 | 0.0048 | 36.8 | 61.3 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,300 RPM × 0.091 mm/rev = 210 mm/min.
Worked example: 3.8 mm drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.1496 ≈ 2,300 RPM.
- Feed for a 0.150 in drill in mild steel ≈ 0.0036 in/rev.
- IPM = 2,300 × 0.0036 = 8.28 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.449 in (11.4 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.748 in (19 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.197 in (30.4 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 3.8 mm drill
- M4x0.5 — form (roll) tap, 65% thread
Nearest drills
- #25: 0.1495 in / 3.797 mm (-0.0001 in)
- #24: 0.1520 in / 3.861 mm (+0.0024 in)
- #26: 0.1470 in / 3.734 mm (-0.0026 in)
- 3.9 mm: 0.1535 in / 3.900 mm (+0.0039 in)
Common questions
- What is a 3.8 mm drill in decimal and mm?
- 0.1496 in, or 3.800 mm; nearest fractional drill: 5/32" (0.1563 in, +0.0066 in); nearest number / letter drill: #25 (0.1495 in, -0.0001 in).
- What RPM for a 3.8 mm drill in steel?
- In low-carbon steel (1018) an HSS 3.8 mm drill (0.1496 in) runs about 2,300 RPM at 90 SFM; a carbide drill about 7,660 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a 3.8 mm drill?
- About 0.0036 in/rev in mild steel, 0.0035 in/rev in aluminum and 0.0024 in/rev in 304 stainless. At 2,300 RPM that is 8.28 IPM in steel (IPM = RPM × IPR).
- What RPM for a 3.8 mm drill in aluminum?
- 6,380 RPM with HSS (250 SFM) or up to 15,320 RPM with carbide (600 SFM), feeding about 0.0035 in/rev.
- What tap uses a 3.8 mm drill?
- M4x0.5 (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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