Taps & Dies Fractional Taps
Triumph HSS fractional taps for cutting bolt-size internal threads in metal. 63 ThunderTap Taper, Plug and Bottoming taps in coarse (NC) and fine (NF) pitches.
Choosing a fractional tap
Fractional taps cut the internal threads for standard bolts and cap screws. This range is 63 Triumph HSS ThunderTaps, each listed by thread size and pitch: 3/8-16 NC, 5/16-24 NF, 7/8-14 NF, 1-1/8-7 NC and so on. Each size comes in Taper, Plug and Bottoming styles.
Most general work calls for a plug tap. Use a taper tap when you want an easy start, and a bottoming tap to get threads close to the bottom of a blind hole. Coarse (NC) and fine (NF) are different pitches for the same diameter, so check the bolt before you order.
Tapping tips
A tap drill chart gives the exact drill size. As a rule, it is the major diameter minus the pitch. Drill straight, lubricate, and turn the tap back a quarter turn every half turn or so to break the chip. Large sizes take real torque, so use a tap wrench that fits and keep the tap square.
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Common questions
Which style do I need, taper, plug or bottoming?
Plug works for most jobs. Taper starts easiest. Bottoming is for blind holes where threads need to run close to the bottom, and it is usually used after a plug tap has started the thread.
What size hole do I drill before tapping?
Use a tap drill chart for the exact size. As a rough rule, the drill is the tap's major diameter minus the pitch, which is 1 divided by the threads per inch.
Should I choose NC or NF?
Match the thread you are mating with. NC is the coarse pitch for a given diameter, such as 3/8-16, and NF is the fine pitch, such as 3/8-24. They are not interchangeable.
Buying for a crew?
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