4.2 mm drill size
A 4.2 mm metric drill is 0.1653 in (4.200 mm). It is the cut tap, 75% thread drill for M5×0.8.
- Decimal inch
- 0.1653
- Millimeters
- 4.200
- Nearest 1/64
- 11/64" (-0.0065)
- Type
- metric drill
Nearest equivalents in other systems
Speeds and feeds: in mild steel an HSS drill starts at about 2,080 RPM and 0.0041 in/rev (8.53 IPM); in 6061 aluminum about 5,780 RPM.
4.2 mm drill speeds and feeds by material
Jobber-length twist drill, D = 0.1653 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 | 5,780 | 600 | 13,860 | 0.0039 | 22.5 | 54.0 |
| Brass / free-machining | 150 | 3,470 | 400 | 9,240 | 0.0033 | 11.4 | 30.5 |
| Low-carbon steel (1018) | 90 | 2,080 | 300 | 6,930 | 0.0041 | 8.53 | 28.4 |
| Alloy steel (4140, annealed) | 70 | 1,620 | 250 | 5,780 | 0.0041 | 6.64 | 23.7 |
| Stainless 304 | 40 | 920 | 150 | 3,470 | 0.0027 | 2.48 | 9.37 |
| Gray cast iron | 80 | 1,850 | 250 | 5,780 | 0.0027 | 5.00 | 15.6 |
| Titanium 6Al-4V | 25 | 580 | 100 | 2,310 | 0.0020 | 1.16 | 4.62 |
| Plastics (acetal) | 300 | 6,930 | 500 | 11,550 | 0.0047 | 32.6 | 54.3 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 2,080 RPM × 0.104 mm/rev = 217 mm/min.
Worked example: 4.2 mm drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.1653 ≈ 2,080 RPM.
- Feed for a 0.165 in drill in mild steel ≈ 0.0041 in/rev.
- IPM = 2,080 × 0.0041 = 8.53 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.496 in (12.6 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.827 in (21 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.323 in (33.6 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 4.2 mm drill
- M5×0.8 — cut tap, 75% thread · tap speeds and feeds
Nearest drills
- #19: 0.1660 in / 4.216 mm (+0.0006 in)
- 4.1 mm: 0.1614 in / 4.100 mm (-0.0039 in)
- 4.3 mm: 0.1693 in / 4.300 mm (+0.0039 in)
- #18: 0.1695 in / 4.305 mm (+0.0042 in)
Common questions
- What is a 4.2 mm drill in decimal and mm?
- 0.1653 in, or 4.200 mm; nearest fractional drill: 11/64" (0.1719 in, +0.0065 in); nearest number / letter drill: #19 (0.1660 in, +0.0006 in).
- What RPM for a 4.2 mm drill in steel?
- In low-carbon steel (1018) an HSS 4.2 mm drill (0.1653 in) runs about 2,080 RPM at 90 SFM; a carbide drill about 6,930 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a 4.2 mm drill?
- About 0.0041 in/rev in mild steel, 0.0039 in/rev in aluminum and 0.0027 in/rev in 304 stainless. At 2,080 RPM that is 8.53 IPM in steel (IPM = RPM × IPR).
- What RPM for a 4.2 mm drill in aluminum?
- 5,780 RPM with HSS (250 SFM) or up to 13,860 RPM with carbide (600 SFM), feeding about 0.0039 in/rev.
- What tap uses a 4.2 mm drill?
- M5×0.8 (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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