#1 drill size
A #1 number (wire-gauge) drill is 0.2280 in (5.791 mm). It is the form (roll) tap, 65% thread drill for 1/4-20.
- Decimal inch
- 0.2280
- Millimeters
- 5.791
- Nearest 1/64
- 15/64" (-0.0064)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 15/64" | 0.2344 | 5.953 | +0.0064 in |
| Metric | 5.8 mm | 0.2283 | 5.800 | +0.0003 in |
Speeds and feeds: in mild steel an HSS drill starts at about 1,510 RPM and 0.0059 in/rev (8.91 IPM); in 6061 aluminum about 4,190 RPM.
#1 drill speeds and feeds by material
Jobber-length twist drill, D = 0.2280 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 | 4,190 | 600 | 10,050 | 0.0054 | 22.6 | 54.3 |
| Brass / free-machining | 150 | 2,510 | 400 | 6,700 | 0.0047 | 11.8 | 31.5 |
| Low-carbon steel (1018) | 90 | 1,510 | 300 | 5,030 | 0.0059 | 8.91 | 29.7 |
| Alloy steel (4140, annealed) | 70 | 1,170 | 250 | 4,190 | 0.0059 | 6.90 | 24.7 |
| Stainless 304 | 40 | 670 | 150 | 2,510 | 0.0039 | 2.61 | 9.79 |
| Gray cast iron | 80 | 1,340 | 250 | 4,190 | 0.0040 | 5.36 | 16.8 |
| Titanium 6Al-4V | 25 | 420 | 100 | 1,680 | 0.0027 | 1.13 | 4.54 |
| Plastics (acetal) | 300 | 5,030 | 500 | 8,380 | 0.0042 | 21.1 | 35.2 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,510 RPM × 0.150 mm/rev = 226 mm/min.
Worked example: #1 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.2280 ≈ 1,510 RPM.
- Feed for a 0.228 in drill in mild steel ≈ 0.0059 in/rev.
- IPM = 1,510 × 0.0059 = 8.91 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.684 in (17.4 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 1.140 in (29 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.824 in (46.3 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 #1 drill
- 1/4-20 — form (roll) tap, 65% thread · tap speeds and feeds
- 1/4-28 — cut tap, 50% thread · tap speeds and feeds
- 1/4-32 — cut tap, 50% thread
Nearest drills
- 5.8 mm: 0.2283 in / 5.800 mm (+0.0003 in)
- 5.7 mm: 0.2244 in / 5.700 mm (-0.0036 in)
- 5.9 mm: 0.2323 in / 5.900 mm (+0.0043 in)
- Letter A: 0.2340 in / 5.944 mm (+0.0060 in)
Common questions
- What is a #1 drill in decimal and mm?
- 0.2280 in, or 5.791 mm; nearest fractional drill: 15/64" (0.2344 in, +0.0064 in); nearest metric drill: 5.8 mm (0.2283 in, +0.0003 in).
- What RPM for a #1 drill in steel?
- In low-carbon steel (1018) an HSS #1 drill (0.2280 in) runs about 1,510 RPM at 90 SFM; a carbide drill about 5,030 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #1 drill?
- About 0.0059 in/rev in mild steel, 0.0054 in/rev in aluminum and 0.0039 in/rev in 304 stainless. At 1,510 RPM that is 8.91 IPM in steel (IPM = RPM × IPR).
- What RPM for a #1 drill in aluminum?
- 4,190 RPM with HSS (250 SFM) or up to 10,050 RPM with carbide (600 SFM), feeding about 0.0054 in/rev.
- What tap uses a #1 drill?
- 1/4-20 (form (roll) tap, 65% thread); 1/4-28 (cut tap, 50% thread); 1/4-32 (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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