14 x 28, National Fine Thread, Fractional Tap, Carbon Steel, Ideal For Routine Maintenance, Repair Work For Rethreading Where High Accuracy Tolerance Thread Is Not Critical, Straight Flutes Are Ground To Provide Rapid Chip Removal For Efficient Threading, Designed For Hand Threading Work In A Variety Of Materials Taps Produce A Class 2B Thread, Use Drill Bit 3 Or 1364