#68 drill size
A #68 number (wire-gauge) drill is 0.0310 in (0.787 mm).
- Decimal inch
- 0.0310
- Millimeters
- 0.787
- Nearest 1/64
- 1/32" (-0.0003)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 1/32" | 0.0313 | 0.794 | +0.0003 in |
| Metric | 0.8 mm | 0.0315 | 0.800 | +0.0005 in |
Speeds and feeds: in mild steel an HSS drill starts at about 11,090 RPM and 0.0007 in/rev (7.76 IPM); in 6061 aluminum about 30,800 RPM.
#68 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0310 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 | 30,800 | 600 | 73,930 | 0.0007 | 21.6 | 51.8 |
| Brass / free-machining | 150 | 18,480 | 400 | 49,290 | 0.0006 | 11.1 | 29.6 |
| Low-carbon steel (1018) | 90 | 11,090 | 300 | 36,970 | 0.0007 | 7.76 | 25.9 |
| Alloy steel (4140, annealed) | 70 | 8,630 | 250 | 30,800 | 0.0007 | 6.04 | 21.6 |
| Stainless 304 | 40 | 4,930 | 150 | 18,480 | 0.0005 | 2.47 | 9.24 |
| Gray cast iron | 80 | 9,860 | 250 | 30,800 | 0.0005 | 4.93 | 15.4 |
| Titanium 6Al-4V | 25 | 3,080 | 100 | 12,320 | 0.0004 | 1.23 | 4.93 |
| Plastics (acetal) | 300 | 36,970 | 500 | 61,610 | 0.0013 | 48.1 | 80.1 |
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, 11,090 RPM × 0.018 mm/rev = 197 mm/min.
Worked example: #68 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0310 ≈ 11,090 RPM.
- Feed for a 0.031 in drill in mild steel ≈ 0.0007 in/rev.
- IPM = 11,090 × 0.0007 = 7.76 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.093 in (2.4 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.155 in (3.9 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.248 in (6.3 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 #68 drill
No standard UNC, UNF or metric tap in our tables calls for a #68 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 1/32": 0.0313 in / 0.794 mm (+0.0003 in)
- 0.8 mm: 0.0315 in / 0.800 mm (+0.0005 in)
- #67: 0.0320 in / 0.813 mm (+0.0010 in)
- 0.75 mm: 0.0295 in / 0.750 mm (-0.0015 in)
Common questions
- What is a #68 drill in decimal and mm?
- 0.0310 in, or 0.787 mm; nearest fractional drill: 1/32" (0.0313 in, +0.0003 in); nearest metric drill: 0.8 mm (0.0315 in, +0.0005 in).
- What RPM for a #68 drill in steel?
- In low-carbon steel (1018) an HSS #68 drill (0.0310 in) runs about 11,090 RPM at 90 SFM; a carbide drill about 36,970 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #68 drill?
- About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 11,090 RPM that is 7.76 IPM in steel (IPM = RPM × IPR).
- What RPM for a #68 drill in aluminum?
- 30,800 RPM with HSS (250 SFM) or up to 73,930 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.
- What size is a #68 drill?
- 0.0310 in / 0.787 mm. The nearest other drills are 1/32" (0.0313 in), 0.8 mm (0.0315 in), #67 (0.0320 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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