Post on 12-Jul-2020
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
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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.
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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
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Hand Taps in Action
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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
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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
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A Round Die in Action
Step 1
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A Round Die in Action
Step 2
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A Round Die in Action
Step 3
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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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