11/32" drill size

    A 11/32" fractional drill is 0.3438 in (8.731 mm). It is the cut tap, 75% thread drill for 3/8-32.

    Decimal inch
    0.3438
    Millimeters
    8.731
    Nearest 1/64
    11/32" (+0.0000)
    Type
    fractional drill

    Nearest equivalents in other systems

    Drills closest to 11/32"
    SystemDrillInchmmDifference
    Number / letterLetter S0.34808.839+0.0043 in
    Metric8.7 mm0.34258.700-0.0012 in

    Speeds and feeds: in mild steel an HSS drill starts at about 1,000 RPM and 0.0088 in/rev (8.80 IPM); in 6061 aluminum about 2,780 RPM.

    11/32" drill speeds and feeds by material

    Jobber-length twist drill, D = 0.3438 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

    11/32" drilling speeds
    MaterialHSS SFMHSS RPMCarbide SFMCarbide RPMFeed (in/rev)HSS IPMCarbide IPM
    Aluminum (6061)2502,7806006,6700.007922.052.7
    Brass / free-machining1501,6704004,4400.006010.026.6
    Low-carbon steel (1018)901,0003003,3300.00888.8029.3
    Alloy steel (4140, annealed)707802502,7800.00957.4126.4
    Stainless 304404401501,6700.00582.559.69
    Gray cast iron808902502,7800.00605.3416.7
    Titanium 6Al-4V252801001,1100.00391.094.33
    Plastics (acetal)3003,3305005,5600.004816.026.7

    Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 1,000 RPM × 0.224 mm/rev = 224 mm/min.

    Worked example: 11/32" drill in 1018 steel

    1. HSS drill in low-carbon steel: 90 SFM.
    2. RPM = 3.82 × 90 ÷ 0.3438 ≈ 1,000 RPM.
    3. Feed for a 0.344 in drill in mild steel ≈ 0.0088 in/rev.
    4. IPM = 1,000 × 0.0088 = 8.80 IPM.

    Peck cycle by hole depth

    11/32" drill: depth and canned cycle
    DepthCyclePeckNote
    3×D = 1.031 in (26.2 mm)G81 (no peck)NoneUp to 3×D a sharp drill clears chips on its own.
    5×D = 1.719 in (43.7 mm)G73 chip-break1 × DChip-break pecks; full retract if chips pack (soft aluminum, stainless).
    8×D = 2.750 in (69.8 mm)G83 full retract0.5-1 × D, shrinking with depthRetract to clear chips; reduce feed ~10-20% past 5×D.

    Taps that use a 11/32" drill

    • 3/8-32 — cut tap, 75% thread

    Nearest drills

    • 8.7 mm: 0.3425 in / 8.700 mm (-0.0012 in)
    • 8.8 mm: 0.3465 in / 8.800 mm (+0.0027 in)
    • Letter S: 0.3480 in / 8.839 mm (+0.0043 in)
    • Letter R: 0.3390 in / 8.611 mm (-0.0047 in)
    Drill speed calculator, prefilled for 11/32"Drill finder: sizes near 11/32"Fractional drill chartDecimal equivalent chart

    Common questions

    What is a 11/32" drill in decimal and mm?
    0.3438 in, or 8.731 mm; nearest number / letter drill: Letter S (0.3480 in, +0.0043 in); nearest metric drill: 8.7 mm (0.3425 in, -0.0012 in).
    What RPM for a 11/32" drill in steel?
    In low-carbon steel (1018) an HSS 11/32" drill (0.3438 in) runs about 1,000 RPM at 90 SFM; a carbide drill about 3,330 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
    What feed for a 11/32" drill?
    About 0.0088 in/rev in mild steel, 0.0079 in/rev in aluminum and 0.0058 in/rev in 304 stainless. At 1,000 RPM that is 8.80 IPM in steel (IPM = RPM × IPR).
    What RPM for a 11/32" drill in aluminum?
    2,780 RPM with HSS (250 SFM) or up to 6,670 RPM with carbide (600 SFM), feeding about 0.0079 in/rev.
    What tap uses a 11/32" drill?
    3/8-32 (cut tap, 75% 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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