#45 drill size
A #45 number (wire-gauge) drill is 0.0820 in (2.083 mm). It is the cut tap, 75% thread drill for 3-56.
- Decimal inch
- 0.0820
- Millimeters
- 2.083
- Nearest 1/64
- 5/64" (+0.0039)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 5/64" | 0.0781 | 1.984 | -0.0039 in |
| Metric | 2.1 mm | 0.0827 | 2.100 | +0.0007 in |
Speeds and feeds: in mild steel an HSS drill starts at about 4,190 RPM and 0.0019 in/rev (7.96 IPM); in 6061 aluminum about 11,650 RPM.
#45 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0820 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 | 11,650 | 600 | 27,950 | 0.0019 | 22.1 | 53.1 |
| Brass / free-machining | 150 | 6,990 | 400 | 18,630 | 0.0016 | 11.2 | 29.8 |
| Low-carbon steel (1018) | 90 | 4,190 | 300 | 13,970 | 0.0019 | 7.96 | 26.5 |
| Alloy steel (4140, annealed) | 70 | 3,260 | 250 | 11,650 | 0.0019 | 6.19 | 22.1 |
| Stainless 304 | 40 | 1,860 | 150 | 6,990 | 0.0013 | 2.42 | 9.09 |
| Gray cast iron | 80 | 3,730 | 250 | 11,650 | 0.0012 | 4.48 | 14.0 |
| Titanium 6Al-4V | 25 | 1,160 | 100 | 4,660 | 0.0010 | 1.16 | 4.66 |
| Plastics (acetal) | 300 | 13,970 | 500 | 23,290 | 0.0033 | 46.1 | 76.9 |
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, 4,190 RPM × 0.048 mm/rev = 202 mm/min.
Worked example: #45 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0820 ≈ 4,190 RPM.
- Feed for a 0.082 in drill in mild steel ≈ 0.0019 in/rev.
- IPM = 4,190 × 0.0019 = 7.96 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.246 in (6.2 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.410 in (10.4 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.656 in (16.7 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 #45 drill
- 3-56 — cut tap, 75% thread · tap speeds and feeds
- 1-72 — Helicoil / STI insert (#1-72×1D) · tap speeds and feeds
Nearest drills
- 2.1 mm: 0.0827 in / 2.100 mm (+0.0007 in)
- #46: 0.0810 in / 2.057 mm (-0.0010 in)
- 2.05 mm: 0.0807 in / 2.050 mm (-0.0013 in)
- 2.15 mm: 0.0847 in / 2.150 mm (+0.0027 in)
Common questions
- What is a #45 drill in decimal and mm?
- 0.0820 in, or 2.083 mm; nearest fractional drill: 5/64" (0.0781 in, -0.0039 in); nearest metric drill: 2.1 mm (0.0827 in, +0.0007 in).
- What RPM for a #45 drill in steel?
- In low-carbon steel (1018) an HSS #45 drill (0.0820 in) runs about 4,190 RPM at 90 SFM; a carbide drill about 13,970 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #45 drill?
- About 0.0019 in/rev in mild steel, 0.0019 in/rev in aluminum and 0.0013 in/rev in 304 stainless. At 4,190 RPM that is 7.96 IPM in steel (IPM = RPM × IPR).
- What RPM for a #45 drill in aluminum?
- 11,650 RPM with HSS (250 SFM) or up to 27,950 RPM with carbide (600 SFM), feeding about 0.0019 in/rev.
- What tap uses a #45 drill?
- 3-56 (cut tap, 75% thread); 1-72 (Helicoil / STI insert (#1-72×1D)).
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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