#72 drill size
A #72 number (wire-gauge) drill is 0.0250 in (0.635 mm).
- Decimal inch
- 0.0250
- Millimeters
- 0.635
- Nearest 1/64
- 1/32" (-0.0062)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 1/32" | 0.0313 | 0.794 | +0.0063 in |
| Metric | 0.65 mm | 0.0256 | 0.650 | +0.0006 in |
Speeds and feeds: in mild steel an HSS drill starts at about 13,750 RPM and 0.0007 in/rev (9.63 IPM); in 6061 aluminum about 38,200 RPM.
#72 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0250 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 | 38,200 | 600 | 91,670 | 0.0007 | 26.7 | 64.2 |
| Brass / free-machining | 150 | 22,920 | 400 | 61,120 | 0.0006 | 13.8 | 36.7 |
| Low-carbon steel (1018) | 90 | 13,750 | 300 | 45,840 | 0.0007 | 9.63 | 32.1 |
| Alloy steel (4140, annealed) | 70 | 10,700 | 250 | 38,200 | 0.0007 | 7.49 | 26.7 |
| Stainless 304 | 40 | 6,110 | 150 | 22,920 | 0.0005 | 3.06 | 11.5 |
| Gray cast iron | 80 | 12,220 | 250 | 38,200 | 0.0005 | 6.11 | 19.1 |
| Titanium 6Al-4V | 25 | 3,820 | 100 | 15,280 | 0.0004 | 1.53 | 6.11 |
| Plastics (acetal) | 300 | 45,840 | 500 | 76,390 | 0.0013 | 59.6 | 99.3 |
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, 13,750 RPM × 0.018 mm/rev = 244 mm/min.
Worked example: #72 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0250 ≈ 13,750 RPM.
- Feed for a 0.025 in drill in mild steel ≈ 0.0007 in/rev.
- IPM = 13,750 × 0.0007 = 9.63 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.075 in (1.9 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.125 in (3.2 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.200 in (5.1 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 #72 drill
No standard UNC, UNF or metric tap in our tables calls for a #72 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 0.65 mm: 0.0256 in / 0.650 mm (+0.0006 in)
- #73: 0.0240 in / 0.610 mm (-0.0010 in)
- #71: 0.0260 in / 0.660 mm (+0.0010 in)
- 0.6 mm: 0.0236 in / 0.600 mm (-0.0014 in)
Common questions
- What is a #72 drill in decimal and mm?
- 0.0250 in, or 0.635 mm; nearest fractional drill: 1/32" (0.0313 in, +0.0063 in); nearest metric drill: 0.65 mm (0.0256 in, +0.0006 in).
- What RPM for a #72 drill in steel?
- In low-carbon steel (1018) an HSS #72 drill (0.0250 in) runs about 13,750 RPM at 90 SFM; a carbide drill about 45,840 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #72 drill?
- About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 13,750 RPM that is 9.63 IPM in steel (IPM = RPM × IPR).
- What RPM for a #72 drill in aluminum?
- 38,200 RPM with HSS (250 SFM) or up to 91,670 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.
- What size is a #72 drill?
- 0.0250 in / 0.635 mm. The nearest other drills are 0.65 mm (0.0256 in), #73 (0.0240 in), #71 (0.0260 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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