#7 drill size
A #7 number (wire-gauge) drill is 0.2010 in (5.105 mm). It is the cut tap, 75% thread drill for 1/4-20.
- Decimal inch
- 0.2010
- Millimeters
- 5.105
- Nearest 1/64
- 13/64" (-0.0021)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 13/64" | 0.2031 | 5.159 | +0.0021 in |
| Metric | 5.1 mm | 0.2008 | 5.100 | -0.0002 in |
Speeds and feeds: in mild steel an HSS drill starts at about 1,710 RPM and 0.0051 in/rev (8.72 IPM); in 6061 aluminum about 4,750 RPM.
#7 drill speeds and feeds by material
Jobber-length twist drill, D = 0.2010 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 | 4,750 | 600 | 11,400 | 0.0048 | 22.8 | 54.7 |
| Brass / free-machining | 150 | 2,850 | 400 | 7,600 | 0.0041 | 11.7 | 31.2 |
| Low-carbon steel (1018) | 90 | 1,710 | 300 | 5,700 | 0.0051 | 8.72 | 29.1 |
| Alloy steel (4140, annealed) | 70 | 1,330 | 250 | 4,750 | 0.0051 | 6.78 | 24.2 |
| Stainless 304 | 40 | 760 | 150 | 2,850 | 0.0034 | 2.58 | 9.69 |
| Gray cast iron | 80 | 1,520 | 250 | 4,750 | 0.0034 | 5.17 | 16.1 |
| Titanium 6Al-4V | 25 | 480 | 100 | 1,900 | 0.0024 | 1.15 | 4.56 |
| Plastics (acetal) | 300 | 5,700 | 500 | 9,500 | 0.0044 | 25.1 | 41.8 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,710 RPM × 0.130 mm/rev = 222 mm/min.
Worked example: #7 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.2010 ≈ 1,710 RPM.
- Feed for a 0.201 in drill in mild steel ≈ 0.0051 in/rev.
- IPM = 1,710 × 0.0051 = 8.72 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.603 in (15.3 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 1.005 in (25.5 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.608 in (40.8 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 #7 drill
- 1/4-20 — cut tap, 75% thread · tap speeds and feeds
- 12-28 — form (roll) tap, 65% thread · tap speeds and feeds
Nearest drills
- 5.1 mm: 0.2008 in / 5.100 mm (-0.0002 in)
- #8: 0.1990 in / 5.055 mm (-0.0020 in)
- 13/64": 0.2031 in / 5.159 mm (+0.0021 in)
- #6: 0.2040 in / 5.182 mm (+0.0030 in)
Common questions
- What is a #7 drill in decimal and mm?
- 0.2010 in, or 5.105 mm; nearest fractional drill: 13/64" (0.2031 in, +0.0021 in); nearest metric drill: 5.1 mm (0.2008 in, -0.0002 in).
- What RPM for a #7 drill in steel?
- In low-carbon steel (1018) an HSS #7 drill (0.2010 in) runs about 1,710 RPM at 90 SFM; a carbide drill about 5,700 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #7 drill?
- About 0.0051 in/rev in mild steel, 0.0048 in/rev in aluminum and 0.0034 in/rev in 304 stainless. At 1,710 RPM that is 8.72 IPM in steel (IPM = RPM × IPR).
- What RPM for a #7 drill in aluminum?
- 4,750 RPM with HSS (250 SFM) or up to 11,400 RPM with carbide (600 SFM), feeding about 0.0048 in/rev.
- What tap uses a #7 drill?
- 1/4-20 (cut tap, 75% thread); 12-28 (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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