taps and dies - drill america...

Taps and DiesDrill America Tool School

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What are Taps and Dies?Taps and dies are cutting tools used to cut new threads and clean or fix existing screw threads.

Tap Die

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Tap and Die Basics● A size is determined by the diameter and

the number of threads per inch○ Example ¼”-20 Tap (or die) means the

diameter is ¼” and the threads per inch (also called TPI) is 20

● Taps and Dies Come in Two Materials○ Carbon Steel for cleaning up or “fixing”

threads○ High speed steel for making new

threads● Multiple styles of taps (next slide)● Two shapes of dies, Hex and Round


Pictured above is a taper, plug and bottoming tap along with hex and round dies.


Types of TapsThe most common types of taps are:● Hand Taps (Bolt Taps)

○ Taper○ Plug○ Bottoming

● NPT Taps (National Pipe Taper)● Spiral Point (Gun Tap)

Less common types of taps:● Acme Taps● NPS Taps (National Pipe Straight)● British Standard● Extension Taps● Nut Taps

To keep things simple we will only discuss the common types of taps in this presentation.

Hand TapsHand Taps are the most versatile taps for hand use.

● Popular for use in general hand tapping

● Appropriate for tapping the vast majority of materials in through or blind holed conditions

● 3 Types - Taper, Plug and Bottoming.

● One of each type makes up a Tap Set

Pictured above is a tap set - 1 taper, 1 plug and 1 bottoming tap.


Taper Plug Bottoming


Taper Taps

● Also called a starter tap● Slightly pointed tip, 7-10 thread chamfer● Starts the thread square with the workpiece● Very gradual cutting action● Most often used when the material to be

tapped is difficult to work (e.g., alloy steel) or the tap is of a very small diameter and thus prone to breakage

● More cutting edges on the workpiece will distribute the load/pressure to cut the threads

Plug Taps

● The most versatile and commonly used type of hand tap

● 3 - 5 thread Chamfer● Generally used in thru holes● Assist in aligning and starting the tap into an

untapped hole● Also used to cut threads until the point of the

tap reaches bottom of the hole● High speed steel taps normally have a center

drilled hole on the shank for aligning purposes

Bottoming Taps

● Flat top with a continuous cutting edge with almost no taper

● 1 - 1-½ thread chamfer● For use in cutting threads to the bottom of a

blind hole● Usually used to cut threads in a hole that has

already been partially threaded using a taper or plug tap

● The tapered end ("tap chamfer") of a bottoming tap is too short to successfully start into an unthreaded hole

Spiral Point (Gun) Taps

● Also called “machine taps” and “gun taps”● Gun taps are used for production with a tapping head● Tap shoots chips ahead of the cutting action, thus

reducing loading and clogging in the flutes. ● They are recommended for use in through or blind

holes which allow for chip accumulation in the bottom of the hole.

● Ideal for threading a wide variety of ductile materials, copper and copper alloys, brass and non-metallics

● Plug style is the standard for gun taps, bottoming is also available



Hand Taps in Action



National Pipe Taper (NPT) Taps

● For use on threaded pipes and pipe fittings

● Commonly called “Pipe Taps”● The size of a Pipe Tap is that of the

pipe fitting to be tapped, not the actual size of the tap

● Not to be confused with NPS which is National Pipe Straight



Round Dies

● Round dies are typically made of high speed steel

● Can be used to make new threads or re-thread

● OD (Outside Diameter) can range from 5/8” - 4”

● A die stock (also called die handle) is required for use. Die stock size corresponds with the die’s OD



A Round Die in Action

Step 1




Step 2




Step 3



Hex Rethreading Dies

● Hex dies are typically made of carbon steel● Can be used to “clean up” or fix damaged

threads● Most cost effective way to clean up threads● Ideal for maintenance in the shop or field● No special die handle is required, normal

wrench works for turning



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