1. Drill America Tool School www.DrillAmerica.net
Taps and Dies
Drill America Tool School

2. What are Taps and Dies? Tap Die
Taps and dies are cutting tools used to cut new threads and clean or fix existing screw threads.
Tap
Die
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3. 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.
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4. Types of Taps The 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.

5. Hand Taps Hand 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
Taper
Plug
Bottoming
Pictured above is a tap set - 1 taper, 1 plug and 1 bottoming tap.
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6. 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

7. 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

8. 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

9. 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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10. Hand Taps in Action
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11. 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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12. 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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13. Step 1 A Round Die in Action
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14. Step 2 A Round Die in Action
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15. Step 3 A Round Die in Action
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16. 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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