#33 drill size

    A #33 number (wire-gauge) drill is 0.1130 in (2.870 mm). It is the cut tap, 75% thread drill for 6-40.

    Decimal inch
    0.1130
    Millimeters
    2.870
    Nearest 1/64
    7/64" (+0.0036)
    Type
    number (wire-gauge) drill

    Nearest equivalents in other systems

    Drills closest to #33
    SystemDrillInchmmDifference
    Fractional7/64"0.10942.778-0.0036 in
    Metric2.85 mm0.11222.850-0.0008 in

    Speeds and feeds: in mild steel an HSS drill starts at about 3,040 RPM and 0.0027 in/rev (8.21 IPM); in 6061 aluminum about 8,450 RPM.

    #33 drill speeds and feeds by material

    Jobber-length twist drill, D = 0.1130 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

    #33 drilling speeds
    MaterialHSS SFMHSS RPMCarbide SFMCarbide RPMFeed (in/rev)HSS IPMCarbide IPM
    Aluminum (6061)2508,45060020,2800.002622.052.7
    Brass / free-machining1505,07040013,5200.002211.229.7
    Low-carbon steel (1018)903,04030010,1400.00278.2127.4
    Alloy steel (4140, annealed)702,3702508,4500.00276.4022.8
    Stainless 304401,3501505,0700.00182.439.13
    Gray cast iron802,7002508,4500.00164.3213.5
    Titanium 6Al-4V258501003,3800.00141.194.73
    Plastics (acetal)30010,14050016,9000.004545.676.0

    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, 3,040 RPM × 0.069 mm/rev = 208 mm/min.

    Worked example: #33 drill in 1018 steel

    1. HSS drill in low-carbon steel: 90 SFM.
    2. RPM = 3.82 × 90 ÷ 0.1130 ≈ 3,040 RPM.
    3. Feed for a 0.113 in drill in mild steel ≈ 0.0027 in/rev.
    4. IPM = 3,040 × 0.0027 = 8.21 IPM.

    Peck cycle by hole depth

    #33 drill: depth and canned cycle
    DepthCyclePeckNote
    3×D = 0.339 in (8.6 mm)G81 (no peck)NoneUp to 3×D a sharp drill clears chips on its own.
    5×D = 0.565 in (14.4 mm)G73 chip-break1 × DChip-break pecks; full retract if chips pack (soft aluminum, stainless).
    8×D = 0.904 in (23 mm)G83 full retract0.5-1 × D, shrinking with depthRetract to clear chips; reduce feed ~10-20% past 5×D.

    Taps that use a #33 drill

    Nearest drills

    • 2.85 mm: 0.1122 in / 2.850 mm (-0.0008 in)
    • 2.9 mm: 0.1142 in / 2.900 mm (+0.0012 in)
    • #34: 0.1110 in / 2.819 mm (-0.0020 in)
    • 2.8 mm: 0.1102 in / 2.800 mm (-0.0028 in)
    Drill speed calculator, prefilled for #33Drill finder: sizes near #33Number drill chartDecimal equivalent chart

    Common questions

    What is a #33 drill in decimal and mm?
    0.1130 in, or 2.870 mm; nearest fractional drill: 7/64" (0.1094 in, -0.0036 in); nearest metric drill: 2.85 mm (0.1122 in, -0.0008 in).
    What RPM for a #33 drill in steel?
    In low-carbon steel (1018) an HSS #33 drill (0.1130 in) runs about 3,040 RPM at 90 SFM; a carbide drill about 10,140 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
    What feed for a #33 drill?
    About 0.0027 in/rev in mild steel, 0.0026 in/rev in aluminum and 0.0018 in/rev in 304 stainless. At 3,040 RPM that is 8.21 IPM in steel (IPM = RPM × IPR).
    What RPM for a #33 drill in aluminum?
    8,450 RPM with HSS (250 SFM) or up to 20,280 RPM with carbide (600 SFM), feeding about 0.0026 in/rev.
    What tap uses a #33 drill?
    6-40 (cut tap, 75% thread); 5-40 (form (roll) tap, 65% thread).

    Nearby drill sizes

    Sources

    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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