2-3/4-4 tap drill size

    Use a 2-1/2 drill (2.5000 in) for a 2-3/4-4 cutting tap at 75% thread.

    Drills for 2-3/4-4 (UNC)
    Tap typeDrillDecimal (in)
    Cutting tap, 75% thread2-1/22.5000
    Cutting tap, 50% thread (hard material)2-19/322.5938
    Roll / form tap, 65% thread2-5/82.6250
    Pitch
    6.35 mm (4 TPI)
    Major Ø
    2.7500
    Pitch Ø
    2.5876
    Minor Ø
    2.4794
    Open the tap drill calculatorRoll tap chartHelicoil chart

    Common questions

    What size drill for a 2-3/4-4 tap?
    Use a 2-1/2 drill (2.5000 in) for a 2-3/4-4 cutting tap at 75% thread.
    What drill for a 2-3/4-4 roll (form) tap?
    About 2.6395 in; the nearest standard drill is 2-5/8. Check your tap maker's table.

    Other UNC sizes

    Drill sizes from Machinery's Handbook and ASME B1.1/B1.13M; roll tap sizes from the form-tap formula. Tap and insert makers' tables are authoritative.

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