2-3/4-8 tap drill size

    Use a 2-5/8 drill (2.6250 in) for a 2-3/4-8 cutting tap at 75% thread.

    Drills for 2-3/4-8 (8UN)
    Tap typeDrillDecimal (in)
    Cutting tap, 75% thread2-5/82.6250
    Cutting tap, 50% thread (hard material)2-21/322.6563
    Roll / form tap, 65% thread2-11/162.6875
    Pitch
    3.175 mm (8 TPI)
    Major Ø
    2.7500
    Pitch Ø
    2.6688
    Minor Ø
    2.6147
    Open the tap drill calculatorRoll tap chartHelicoil chart

    Common questions

    What size drill for a 2-3/4-8 tap?
    Use a 2-5/8 drill (2.6250 in) for a 2-3/4-8 cutting tap at 75% thread.
    What drill for a 2-3/4-8 roll (form) tap?
    About 2.6948 in; the nearest standard drill is 2-11/16. Check your tap maker's table.

    Other 8UN 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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