#15 drill size
A #15 number (wire-gauge) drill is 0.1800 in (4.572 mm).
- Decimal inch
- 0.1800
- Millimeters
- 4.572
- Nearest 1/64
- 3/16" (-0.0075)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 3/16" | 0.1875 | 4.762 | +0.0075 in |
| Metric | 4.6 mm | 0.1811 | 4.600 | +0.0011 in |
Speeds and feeds: in mild steel an HSS drill starts at about 1,910 RPM and 0.0045 in/rev (8.59 IPM); in 6061 aluminum about 5,310 RPM.
#15 drill speeds and feeds by material
Jobber-length twist drill, D = 0.1800 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 | 5,310 | 600 | 12,730 | 0.0042 | 22.3 | 53.5 |
| Brass / free-machining | 150 | 3,180 | 400 | 8,490 | 0.0037 | 11.8 | 31.4 |
| Low-carbon steel (1018) | 90 | 1,910 | 300 | 6,370 | 0.0045 | 8.59 | 28.7 |
| Alloy steel (4140, annealed) | 70 | 1,490 | 250 | 5,310 | 0.0045 | 6.70 | 23.9 |
| Stainless 304 | 40 | 850 | 150 | 3,180 | 0.0030 | 2.55 | 9.54 |
| Gray cast iron | 80 | 1,700 | 250 | 5,310 | 0.0030 | 5.10 | 15.9 |
| Titanium 6Al-4V | 25 | 530 | 100 | 2,120 | 0.0022 | 1.17 | 4.66 |
| Plastics (acetal) | 300 | 6,370 | 500 | 10,610 | 0.0046 | 29.3 | 48.8 |
Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,910 RPM × 0.114 mm/rev = 218 mm/min.
Worked example: #15 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.1800 ≈ 1,910 RPM.
- Feed for a 0.180 in drill in mild steel ≈ 0.0045 in/rev.
- IPM = 1,910 × 0.0045 = 8.59 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.540 in (13.7 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.900 in (22.9 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 1.440 in (36.6 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 #15 drill
No standard UNC, UNF or metric tap in our tables calls for a #15 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 4.6 mm: 0.1811 in / 4.600 mm (+0.0011 in)
- #14: 0.1820 in / 4.623 mm (+0.0020 in)
- 4.5 mm: 0.1772 in / 4.500 mm (-0.0028 in)
- #16: 0.1770 in / 4.496 mm (-0.0030 in)
Common questions
- What is a #15 drill in decimal and mm?
- 0.1800 in, or 4.572 mm; nearest fractional drill: 3/16" (0.1875 in, +0.0075 in); nearest metric drill: 4.6 mm (0.1811 in, +0.0011 in).
- What RPM for a #15 drill in steel?
- In low-carbon steel (1018) an HSS #15 drill (0.1800 in) runs about 1,910 RPM at 90 SFM; a carbide drill about 6,370 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #15 drill?
- About 0.0045 in/rev in mild steel, 0.0042 in/rev in aluminum and 0.0030 in/rev in 304 stainless. At 1,910 RPM that is 8.59 IPM in steel (IPM = RPM × IPR).
- What RPM for a #15 drill in aluminum?
- 5,310 RPM with HSS (250 SFM) or up to 12,730 RPM with carbide (600 SFM), feeding about 0.0042 in/rev.
- What size is a #15 drill?
- 0.1800 in / 4.572 mm. The nearest other drills are 4.6 mm (0.1811 in), #14 (0.1820 in), 4.5 mm (0.1772 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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