15/32" drill size

    A 15/32" fractional drill is 0.4688 in (11.906 mm). It is the cut tap, 75% thread drill for 1/2-28.

    Decimal inch
    0.4688
    Millimeters
    11.906
    Nearest 1/64
    15/32" (+0.0000)
    Type
    fractional drill

    Nearest equivalents in other systems

    Drills closest to 15/32"
    SystemDrillInchmmDifference
    Number / letterLetter Z0.413010.490-0.0558 in
    Metric11.9 mm0.468511.900-0.0003 in

    Speeds and feeds: in mild steel an HSS drill starts at about 730 RPM and 0.0102 in/rev (7.45 IPM); in 6061 aluminum about 2,040 RPM.

    15/32" drill speeds and feeds by material

    Jobber-length twist drill, D = 0.4688 in. RPM = 3.82 × SFM ÷ D, rounded to 10. Feed per rev scales with diameter and material; IPM = RPM × IPR.

    15/32" drilling speeds
    MaterialHSS SFMHSS RPMCarbide SFMCarbide RPMFeed (in/rev)HSS IPMCarbide IPM
    Aluminum (6061)2502,0406004,8900.009619.646.9
    Brass / free-machining1501,2204003,2600.00789.5225.4
    Low-carbon steel (1018)907303002,4400.01027.4524.9
    Alloy steel (4140, annealed)705702502,0400.01136.4423.1
    Stainless 304403301501,2200.00792.619.64
    Gray cast iron806502502,0400.00805.2016.3
    Titanium 6Al-4V252001008100.00480.963.89
    Plastics (acetal)3002,4405004,0700.005814.223.6

    Metric: Vc (m/min) = SFM × 0.3048; feed (mm/rev) = in/rev × 25.4. In steel, 730 RPM × 0.259 mm/rev = 189 mm/min.

    Worked example: 15/32" drill in 1018 steel

    1. HSS drill in low-carbon steel: 90 SFM.
    2. RPM = 3.82 × 90 ÷ 0.4688 ≈ 730 RPM.
    3. Feed for a 0.469 in drill in mild steel ≈ 0.0102 in/rev.
    4. IPM = 730 × 0.0102 = 7.45 IPM.

    Peck cycle by hole depth

    15/32" drill: depth and canned cycle
    DepthCyclePeckNote
    3×D = 1.406 in (35.7 mm)G81 (no peck)NoneUp to 3×D a sharp drill clears chips on its own.
    5×D = 2.344 in (59.5 mm)G73 chip-break1 × DChip-break pecks; full retract if chips pack (soft aluminum, stainless).
    8×D = 3.750 in (95.2 mm)G83 full retract0.5-1 × D, shrinking with depthRetract to clear chips; reduce feed ~10-20% past 5×D.

    Taps that use a 15/32" drill

    Nearest drills

    • 11.9 mm: 0.4685 in / 11.900 mm (-0.0003 in)
    • 12.0 mm: 0.4724 in / 12.000 mm (+0.0037 in)
    • 11.8 mm: 0.4646 in / 11.800 mm (-0.0042 in)
    • 12.1 mm: 0.4764 in / 12.100 mm (+0.0076 in)
    Drill speed calculator, prefilled for 15/32"Drill finder: sizes near 15/32"Fractional drill chartDecimal equivalent chart

    Common questions

    What is a 15/32" drill in decimal and mm?
    0.4688 in, or 11.906 mm; nearest number / letter drill: Letter Z (0.4130 in, -0.0558 in); nearest metric drill: 11.9 mm (0.4685 in, -0.0003 in).
    What RPM for a 15/32" drill in steel?
    In low-carbon steel (1018) an HSS 15/32" drill (0.4688 in) runs about 730 RPM at 90 SFM; a carbide drill about 2,440 RPM at 300 SFM. RPM = 3.82 × SFM ÷ D.
    What feed for a 15/32" drill?
    About 0.0102 in/rev in mild steel, 0.0096 in/rev in aluminum and 0.0079 in/rev in 304 stainless. At 730 RPM that is 7.45 IPM in steel (IPM = RPM × IPR).
    What RPM for a 15/32" drill in aluminum?
    2,040 RPM with HSS (250 SFM) or up to 4,890 RPM with carbide (600 SFM), feeding about 0.0096 in/rev.
    What tap uses a 15/32" drill?
    1/2-28 (cut tap, 75% thread); 1/2-13 (form (roll) tap, 65% thread); 1/2-20 (cut tap, 50% 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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