#88 drill size
A #88 number (wire-gauge) drill is 0.0095 in (0.241 mm).
- Decimal inch
- 0.0095
- Millimeters
- 0.241
- Nearest 1/64
- 1/64" (-0.0061)
- Type
- number (wire-gauge) drill
Nearest equivalents in other systems
| System | Drill | Inch | mm | Difference |
|---|---|---|---|---|
| Fractional | 1/64" | 0.0156 | 0.397 | +0.0061 in |
| Metric | 0.25 mm | 0.0098 | 0.250 | +0.0003 in |
Speeds and feeds: in mild steel an HSS drill starts at about 36,190 RPM and 0.0007 in/rev (25.3 IPM); in 6061 aluminum about 100,520 RPM.
#88 drill speeds and feeds by material
Jobber-length twist drill, D = 0.0095 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 | 100,520 | 600 | 241,250 | 0.0007 | 70.4 | 168.9 |
| Brass / free-machining | 150 | 60,310 | 400 | 160,830 | 0.0006 | 36.2 | 96.5 |
| Low-carbon steel (1018) | 90 | 36,190 | 300 | 120,620 | 0.0007 | 25.3 | 84.4 |
| Alloy steel (4140, annealed) | 70 | 28,150 | 250 | 100,520 | 0.0007 | 19.7 | 70.4 |
| Stainless 304 | 40 | 16,080 | 150 | 60,310 | 0.0005 | 8.04 | 30.2 |
| Gray cast iron | 80 | 32,170 | 250 | 100,520 | 0.0005 | 16.1 | 50.3 |
| Titanium 6Al-4V | 25 | 10,050 | 100 | 40,210 | 0.0004 | 4.02 | 16.1 |
| Plastics (acetal) | 300 | 120,620 | 500 | 201,040 | 0.0013 | 156.8 | 261.4 |
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, 36,190 RPM × 0.018 mm/rev = 643 mm/min.
Worked example: #88 drill in 1018 steel
- HSS drill in low-carbon steel: 90 SFM.
- RPM = 3.82 × 90 ÷ 0.0095 ≈ 36,190 RPM.
- Feed for a 0.009 in drill in mild steel ≈ 0.0007 in/rev.
- IPM = 36,190 × 0.0007 = 25.3 IPM.
Peck cycle by hole depth
| Depth | Cycle | Peck | Note |
|---|---|---|---|
| 3×D = 0.028 in (0.7 mm) | G81 (no peck) | None | Up to 3×D a sharp drill clears chips on its own. |
| 5×D = 0.048 in (1.2 mm) | G73 chip-break | 1 × D | Chip-break pecks; full retract if chips pack (soft aluminum, stainless). |
| 8×D = 0.076 in (1.9 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 #88 drill
No standard UNC, UNF or metric tap in our tables calls for a #88 drill. Use it for clearance, pilot or reamer prep holes.
Nearest drills
- 0.25 mm: 0.0098 in / 0.250 mm (+0.0003 in)
- #89: 0.0091 in / 0.231 mm (-0.0004 in)
- #87: 0.0100 in / 0.254 mm (+0.0005 in)
- #90: 0.0087 in / 0.221 mm (-0.0008 in)
Common questions
- What is a #88 drill in decimal and mm?
- 0.0095 in, or 0.241 mm; nearest fractional drill: 1/64" (0.0156 in, +0.0061 in); nearest metric drill: 0.25 mm (0.0098 in, +0.0003 in).
- What RPM for a #88 drill in steel?
- In low-carbon steel (1018) an HSS #88 drill (0.0095 in) runs about 36,190 RPM at 90 SFM; a carbide drill about 120,620 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
- What feed for a #88 drill?
- About 0.0007 in/rev in mild steel, 0.0007 in/rev in aluminum and 0.0005 in/rev in 304 stainless. At 36,190 RPM that is 25.3 IPM in steel (IPM = RPM × IPR).
- What RPM for a #88 drill in aluminum?
- 100,520 RPM with HSS (250 SFM) or up to 241,250 RPM with carbide (600 SFM), feeding about 0.0007 in/rev.
- What size is a #88 drill?
- 0.0095 in / 0.241 mm. The nearest other drills are 0.25 mm (0.0098 in), #89 (0.0091 in), #87 (0.0100 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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