#70 drill size
A #70 number (wire-gauge) drill is 0.0280 in (0.711 mm).
- Decimal inch
- 0.0280
- Millimeters
- 0.711
- Nearest 1/64
- 1/32" (-0.0032)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 1/32" | 0.0313 | 0.794 | +0.0032 in |
| Metric | 0.7 mm | 0.0276 | 0.700 | -0.0004 in |
Speeds and feeds: in mild steel an HSS drill starts at about 12,280 RPM and 0.0007 in/rev (8.60 IPM); in 6061 aluminum about 34,100 RPM.
#70 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0280 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 | 34,100 | 600 | 81,850 | 0.0007 | 23.9 | 57.3 |
| Brass / free-machining | 150 | 20,460 | 400 | 54,570 | 0.0006 | 12.3 | 32.7 |
| Low-carbon steel (1018) | 90 | 12,280 | 300 | 40,930 | 0.0007 | 8.60 | 28.6 |
| Alloy steel (4140, annealed) | 70 | 9,550 | 250 | 34,100 | 0.0007 | 6.69 | 23.9 |
| Stainless 304 | 40 | 5,460 | 150 | 20,460 | 0.0005 | 2.73 | 10.2 |
| Gray cast iron | 80 | 10,910 | 250 | 34,100 | 0.0005 | 5.46 | 17.1 |
| Titanium 6Al-4V | 25 | 3,410 | 100 | 13,640 | 0.0004 | 1.36 | 5.46 |
| Plastics (acetal) | 300 | 40,930 | 500 | 68,210 | 0.0013 | 53.2 | 88.7 |
Small drills: the computed RPM is above most spindles. Run at your spindle's maximum and keep the feed per rev; feed drops in proportion.
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 12,280 RPM × 0.018 mm/rev = 218 mm/min.
Worked example: #70 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0280 ≈ 12,280 RPM.
- Feed for a 0.028 in drill in mild steel ≈ 0.0007 in/rev.
- IPM = 12,280 × 0.0007 = 8.60 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.084 in (2.1 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.140 in (3.6 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.224 in (5.7 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 #70 drill
No standard UNC, UNF or metric tap in our tables calls for a #70 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 0.7 mm: 0.0276 in / 0.700 mm (-0.0004 in)
- #69: 0.0292 in / 0.742 mm (+0.0012 in)
- 0.75 mm: 0.0295 in / 0.750 mm (+0.0015 in)
- #71: 0.0260 in / 0.660 mm (-0.0020 in)
Common questions
- What is a #70 drill in decimal and mm?
- 0.0280 in, or 0.711 mm; nearest fractional drill: 1/32" (0.0313 in, +0.0032 in); nearest metric drill: 0.7 mm (0.0276 in, -0.0004 in).
- What RPM for a #70 drill in steel?
- In low-carbon steel (1018) an HSS #70 drill (0.0280 in) runs about 12,280 RPM at 90 SFM; a carbide drill about 40,930 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #70 drill?
- About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 12,280 RPM that is 8.60 IPM in steel (IPM = RPM × IPR).
- What RPM for a #70 drill in aluminum?
- 34,100 RPM with HSS (250 SFM) or up to 81,850 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.
- What size is a #70 drill?
- 0.0280 in / 0.711 mm. The nearest other drills are 0.7 mm (0.0276 in), #69 (0.0292 in), 0.75 mm (0.0295 in).
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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