#56 drill size
A #56 number (wire-gauge) drill is 0.0465 in (1.181 mm).
- Decimal inch
- 0.0465
- Millimeters
- 1.181
- Nearest 1/64
- 3/64" (-0.0004)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 3/64" | 0.0469 | 1.191 | +0.0004 in |
| Metric | 1.2 mm | 0.0472 | 1.200 | +0.0007 in |
Speeds and feeds: in mild steel an HSS drill starts at about 7,390 RPM and 0.0011 in/rev (8.13 IPM); in 6061 aluminum about 20,540 RPM.
#56 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0465 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 | 20,540 | 600 | 49,290 | 0.0011 | 22.6 | 54.2 |
| Brass / free-machining | 150 | 12,320 | 400 | 32,860 | 0.0009 | 11.1 | 29.6 |
| Low-carbon steel (1018) | 90 | 7,390 | 300 | 24,640 | 0.0011 | 8.13 | 27.1 |
| Alloy steel (4140, annealed) | 70 | 5,750 | 250 | 20,540 | 0.0011 | 6.33 | 22.6 |
| Stainless 304 | 40 | 3,290 | 150 | 12,320 | 0.0007 | 2.30 | 8.62 |
| Gray cast iron | 80 | 6,570 | 250 | 20,540 | 0.0007 | 4.60 | 14.4 |
| Titanium 6Al-4V | 25 | 2,050 | 100 | 8,210 | 0.0006 | 1.23 | 4.93 |
| Plastics (acetal) | 300 | 24,640 | 500 | 41,070 | 0.0019 | 46.8 | 78.0 |
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, 7,390 RPM × 0.028 mm/rev = 206 mm/min.
Worked example: #56 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0465 ≈ 7,390 RPM.
- Feed for a 0.046 in drill in mild steel ≈ 0.0011 in/rev.
- IPM = 7,390 × 0.0011 = 8.13 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.140 in (3.5 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.232 in (5.9 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.372 in (9.4 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 #56 drill
No standard UNC, UNF or metric tap in our tables calls for a #56 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 3/64": 0.0469 in / 1.191 mm (+0.0004 in)
- 1.2 mm: 0.0472 in / 1.200 mm (+0.0007 in)
- 1.15 mm: 0.0453 in / 1.150 mm (-0.0012 in)
- 1.25 mm: 0.0492 in / 1.250 mm (+0.0027 in)
Common questions
- What is a #56 drill in decimal and mm?
- 0.0465 in, or 1.181 mm; nearest fractional drill: 3/64" (0.0469 in, +0.0004 in); nearest metric drill: 1.2 mm (0.0472 in, +0.0007 in).
- What RPM for a #56 drill in steel?
- In low-carbon steel (1018) an HSS #56 drill (0.0465 in) runs about 7,390 RPM at 90 SFM; a carbide drill about 24,640 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #56 drill?
- About 0.0011 in/rev in mild steel, 0.0011 in/rev in aluminum and 0.0007 in/rev in 304 stainless. At 7,390 RPM that is 8.13 IPM in steel (IPM = RPM × IPR).
- What RPM for a #56 drill in aluminum?
- 20,540 RPM with HSS (250 SFM) or up to 49,290 RPM with carbide (600 SFM), feeding about 0.0011 in/rev.
- What size is a #56 drill?
- 0.0465 in / 1.181 mm. The nearest other drills are 3/64" (0.0469 in), 1.2 mm (0.0472 in), 1.15 mm (0.0453 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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