13 Different Types of Thread Taps
There are many different types of thread taps, and knowing exactly when to use each kind can be a bit like a shot in the dark thanks to varying advantages and disadvantages.
At Xometry, we see a lot of threaded parts, and as a result, we are very familiar with all the different types of taps that can be used to create them. Taps are used to create threaded holes for fasteners, such as screws and bolts. By manually turning the thread tap, threads are created in the pre-drilled holes of the material. Thread taps come in a wide range of options with varying endpoints, tapers, and flutings, with some more ideally suited to certain applications than others.
In this article, we will be tackling 13 different types of thread taps. Let's get started:
1. Hand Taps
A hand tap is a tool used to manually carve an internal thread into a piece of material ready for a screw or bolt to be inserted in. A hand-tap set is usually made up of three types of tap: a plug tap, a bottoming tap, and a taper tap. Hand taps are used across a variety of applications as they are multifaceted and adaptable for use by hand as well as tapping under power. Hand taps are also used in general machine tapping and for the majority of materials that have blind- or through-hole conditions. A key feature of the hand taps in comparison to other types of thread taps is the straight flutes to be used in either a shallow blind hole or through hole.
Plug Tap
A plug tap is a type of hand tap, distinguished from bottoming and taper taps by the length of its cutting chamfer. A plug tap has a five-thread chamfer and slowly removes material in the thread beginning with the smaller diameter of the thread. Plug taps are most commonly used for through holes and where there is enough room at the bottom of a blind hole. One of the main advantages of plug taps is that they are easy to use through holes but provide a more complete set of threads in comparison to taper taps. However, a plug tap is not as well suited to finishing threads in blind holes as bottoming taps are.
Bottoming Tap
A bottoming tap is a type of hand tap used to cut threads. It is important to note that the bottoming tap has the smallest thread chamfer of 1.5 and is used to complete the end portion of a blind hole. You can notice the minimal chamfer in the image below. One of the main advantages of this type of tap is that it can get right to the bottom of a blind hole to complete the threads, unlike plug or taper taps, which have longer leads. However, it is not well suited to removing the majority of material from the hole.
Taper Tap
A taper tap is a form of hand tap used to cut threads into a piece of material. Taper taps have a nine-thread chamfer and have the smallest diameter of all hand taps. Taper taps are usually used as starter taps in blind holes or through-hole applications. One of the advantages of taper taps is that they can remove the majority of material initially; however, they are not particularly suited to completing the bottom of blind holes as they tend to leave incomplete threads. Note the pronounced taper of the tool in the image below:
2. Pipe Tap
Pipe taps are a tool used to carve internal thread into parts that will be fitted to form a pressure-tight joint. Pipe taps come in different varieties, with some designed for hydraulic and gas applications, mechanical joints, and hose couplings. Pipe taps are used specifically for threading pipes and must be used more accurately in comparison to other forms of tapping as they are designed and made to mechanically seal a joint for pressure and prevention of leaks. The image below showcases a pipe tap designed for creating NPT pipe threads:
3. Spiral Flute Tap
Spiral flute tap is a form of thread tap used widely across the manufacturing industry. A spiral flute tap has flutes wrapped around the tap’s axis in a helical or spiral formation. Spiral flute taps are commonly used for tapping threads into blind holes and then pulling the chippings out of the hole in the opposite way to the tapping direction. In comparison to hand taps, spiral flute taps do not offer as strong of a cutting edge and have spiral-shaped flutes. You can notice the helical design of the flutes in the following image:
4. Gas Tap
A gas tap is a type of pipe tap. It is commonly used to cut deep threads that comply with specifications for use in gas and hydraulic systems. Gas taps are ideally suited for both conical and cylindrical shaped holes due to their one- or two-thread chamfers, unlike the much wider nine-thread chamfer taper tap.
5. Machine Tap
Machine taps are used for threading and have grown in popularity and importance recently in line with the increased use of machinery in production. Threading tools used in these machines are now required to be increasingly wear-resistant and durable. Machine taps are used in automated machining processes like CNC machining and are suited to both blind holes and through holes. Machine taps are used for hard materials, unlike spiral flute taps. The machine tap in the image below has a titanium-nitride coating on the cutting end, which helps reduce tool wear and increase it's longevity:
6. Thread-Forming Tap
Thread Forming or fluteless taps don’t cut threads at all. Instead, they cold form them. Threads made this way are often called “rolled” threads. With this process, the metal is pushed out of the way and compressed into position rather than being cut. There are no chips to remove. As a result, the taps themselves are less likely to break, and the threads they make are stronger.
We recommend using form taps over cutting taps when possible, as long as the material isn't too hard for thread forming. While many believe they’re only good for soft materials like aluminum, they can actually be used on materials up to a hardness of 36 HRC, which is about 340 BHN. That covers a surprisingly wide range of materials including a lot of steels.
Pro Tip:
Form taps require different feeds and speeds, as well as different starting hole sizes, so be aware of that before using one. Another minor hiccup with quite a few of the roll-forming taps…unless they have a groove to allow cutting oil to escape, or there is no room at the root or crest of the thread, the oil can build up back pressure as the tap goes in, and eventually act like a solid plug blocking further entry of the tap into the hole.
7. Master Tap
A master tap is a variety of threading tap and is widely used across a range of industries. Master taps are known for their universality and diversity and are most commonly used to cut clean threads in strong and hard materials. Master taps are similar to taper taps, however the key difference is in the number of flutes. The master tap has more cutting faces and on average 7 to 10 flutes.
8. Combined Drill and Tap
A combined drill and tap enables the manufacturer to drill the hole and tap threads in one operation, without the need to switch tools, saving both time and money on a production drilling job. It can be used for a variety of materials, including: aluminum, malleable iron, and brass. Similar to a spiral flute, this implement has a helical flute design. Below is an example of a combination drill and tap:
9. Solid Carbide Tap
Solid carbide taps are threading implements made of composite material that consists of sintered ultra-fine tungsten carbides. They are commonly used on hard materials as solid carbide has an extremely high hardness and wear resistance. One of the key benefits of solid carbide taps is the long life span of this tool, even in more challenging working environments.
10. Extension Tap
Extension taps provide an alternative form of thread tap. Due to their long shank on top of the body, extension taps are commonly used to reach more inaccessible holes, for example, the hub of a pulley. The extension tap is very similar to hand taps. Note the extra long shank of the tap in the image below:
11. Spiral Point Tap
A spiral point tap is an alternative form of threading tap used to create threads into a material. By its design, the spiral point tap is used in situations in which higher tapping speeds are required, with lower power to drive and greater strength than other threading taps. In comparison to conventional taps, a spiral point tap has a shallower flute passage, enabling the spiral point tap greater cross-sectional area. While they may be considered very similar compared to a straight flute tap as they share the same general physical dimensions, the key differentiator is the cutting face of the spiral point tap, which can be seen in the image below:
12. Stay Bolt Tap
A stay bolt tap is a type of thread tap, roughly 15–20 inches long, that is designed to cut threads in drilled holes for threaded machine screws or threaded bolts to be screwed in. Stay bolt taps were commonly used in the application of locomotive boilers, predominantly in the repair and installation of fireboxes in steam locomotives. The distinct feature of this thread tap is that it threads holes that match the diameter of a stay bolt nut.
13. Interrupted Thread Tap
These thread taps only have a tooth for every other thread. The idea is to provide improved chip extraction. Removing every other tooth helps break chips and also provides more room for the chip to escape and for lubricant to come in and do its job. The image below shows an example of an NPT pipe tap with interrupted teeth:
The markings typically will include:
- Nominal Size: This is the description of the thread size that tap will make.
- Thread Form Symbol: This describes the thread family.
- Tap Material: Usually Carbide or HSS
- Pitch Diameter Limit: Tells what tolerance thread will be made.
Pitch Diameter Limits (Threads < 1″ in diameter)
L1 = Basic to Basic minus .0005
H1 = Basic to Basic plus .0005
H2 = Basic plus .0005 to Basic plus .0010
H3 = Basic plus .0010 to Basic plus .0015
H4 = Basic plus .0015 to Basic plus .0020
H5 = Basic plus .0020 to Basic plus .0025
H6 = Basic plus .0025 to Basic plus .0030
Note: You can find these limits in G-Wizard’s thread database too.
Choosing a Thread Tap To Use
When choosing a thread tap to use, it is important to consider four main factors to maximize the chances of a successful threading process. Firstly, the type of workpiece. Different materials have differing levels of firmness; therefore the tap type varies as some have distinct features that make them more suitable for certain materials. For example, a machine tap is likely to work better on harder materials, whereas a fluteless tap is better suited for softer metals. Secondly, the tap material must be taken into account. For instance, carbide steel taps can cut threads very quickly and are strong for hard materials such as cast iron. Thirdly, the type of hole is important in choosing a thread tap as the taps have a range of thread chamfers. For example, taps with 1–3 thread chamfers are capable of making deeper holes. Fourthly, the cutting speed is important to factor in when choosing a thread tap as some taps are specially designed for high-speed production. Should speed be a crucial factor, the best type of thread taps are spiral fluted taps.
How Xometry Can Help
At Xometry, our diverse global manufacturing network has experience using all sorts of taps and cutting tools to create threads in parts. We cover everything from standard unified national and metric threads to fine-pitch optical threads and even custom thread forms. If you have custom parts that require threading, we can make them! Get started by uploading your design files to the Xometry Instant Quoting Engine® and get an instant quote today!
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