Threading is a crucial process in machining and metalworking, as it plays a key role in creating strong, secure connections between parts. Therefore, using the right tap is essential for achieving precise, reliable threads. In this blog, we will explore the different types of taps, their components, and how to use them effectively for threading. Furthermore, we’ll discuss how to choose the right tap, understand thread tap sizes, and discover their various applications. Finally, we’ll compare taps and dies to help you understand their differences and when to use each tool. Let’s dive into the essential guide on taps and threading!
What is a Thread Tap?
A thread tap is a cutting tool used to create internal threads, or taps, in a hole. By enabling the formation of threads inside a workpiece, it allows screws or bolts to be securely fastened. The tap works by removing material from the hole to form the desired thread profile. Additionally, taps come in various sizes and designs, depending on the type of thread being created and the material being worked on. They commonly find uses in metalworking, woodworking, and plastic fabrication to prepare holes for threaded fasteners, ensuring strong, secure connections.
Parts of a Thread Tap
A thread tap consists of several key components, each playing a specific role in the threading process:
- Shank: The portion of the tap that fits into the machine or tool holder. It is typically smooth and cylindrical, allowing for easy insertion into a chuck or collet.
- Tang: A small extension at the end of the shank, designed to provide a secure grip in the chuck or holder.
- Body: The main section of the tap, which includes the shank, flutes, threads, and other components. It provides strength and stability during the cutting process.
- Flutes: Grooves running along the length of the tap. These grooves help clear chips and debris, ensuring an efficient and clean threading process.
- Land: The flat surface between the cutting edges of the threads. It offers support and stability during the cutting action.
- Heel: The edge at the bottom of the cutting face, designed to minimize friction and promote smooth cutting.
- Cutting Face: The area where the cutting edges come into contact with the material to form internal threads. The sharpness and design of this face are crucial for producing high-quality threads.
- Threads (Cutting Teeth): The threaded section of the tap containing sharp cutting edges that create internal threads within the hole. The design and spacing of these threads vary depending on the type of tap.
- Point: The tapered end of the tap that initiates the cutting process. It helps guide the tap into the hole and begins the formation of the threads.
- Neck: Positioned just above the cutting threads, the neck provides clearance for the tap, ensuring that the cutting threads stay sharp and effective.
- Back Taper: A slight taper at the base of the tap, which reduces friction and makes it easier to remove the tap after threading.
How To Use a Tap for Threading?
Using a tap for threading involves several steps to ensure accurate, clean threads. Here’s a step-by-step guide on how to use a tap for threading:
1. Select the Right Tap and Drill Bit:
Choose a tap that matches the desired thread size and type for your project. And then select an appropriate drill bit size for the hole, as the hole diameter must match the tap’s specifications for optimal threading.
2. Prepare the Hole:
Drill the hole to the required depth and diameter. The hole should be slightly smaller than the tap’s major diameter to ensure proper thread formation. If necessary, use a center punch to mark the drilling location.
3. Lubricate the Tap:
Apply cutting oil or lubricant to the tap to reduce friction and prevent overheating. This will also promote achieving cleaner threads and extend the life of the tap.
4. Insert the Tap into the Holder:
Secure the tap into a tap wrench or machine tool holder. Ensure the tap is aligned correctly and is perpendicular to the surface to avoid misalignment during the threading process.
5. Start the Tapping Process:
Gently begin turning the tap clockwise into the hole by hand or with a machine. Apply consistent pressure but avoid forcing the tap. It should engage the material slowly and start cutting the threads. For manual tapping, turn the tap wrench with steady, even pressure. For machine tapping, use the machine’s settings to control the tap’s feed rate.
6. Back the Tap Out Periodically:
To prevent chips from clogging the flutes and to reduce friction, back the tap out slightly after every full rotation or after a few turns. This contributes to clearing the debris and ensures smooth cutting.
7. Continue Tapping to Desired Depth:
Continue turning the tap into the hole until you reach the desired thread depth. Keep an eye on the tap’s depth limitations, which are usually marked on the tap or specified by the required thread engagement.
Types of Taps for Threading
Here are the main types of taps for threading, each tailored to specific purposes according to the material, hole configuration, and desired thread characteristics.
1. Plug Taps
A plug tap has a five-thread chamfer that gradually cuts material, starting with a smaller diameter, to form the thread. It is ideal for both through holes and blind holes where there is enough space at the bottom. While it creates a more complete thread than taper taps, it’s not as effective for finishing threads in blind holes, which is where bottoming taps excel. Typically, a plug tap follows a taper tap, as it refines the thread depth and shape, providing a stronger cutting action with its 3-5 tapered threads.
2. Taper Taps
Taper taps have a gradual taper with 8-10 thread chamfers, making them suitable for starting threads in both blind and through holes, especially in harder materials. They effectively remove material early; however, they cannot reach full thread depth. Therefore, plug or bottoming taps typically follow them for completion.
3. Bottoming Taps
Bottoming taps cut threads all the way to the bottom of blind holes, ensuring full thread depth. With a small chamfer of 1-2 threads, they reach the hole’s base and complete the threading. Typically used as the final step in the process, bottoming taps clean and refine previously cut threads, leaving a smooth, fully formed finish.
4. Spiral Point Tap
Spiral point taps are designed to work efficiently on hard materials, providing faster performance with less power required. They create shallow grooves, which enable the removal of more material in a single pass. Although they share a similar shape to straight flute taps, their spiral cutting face sets them apart, allowing for better chip removal and smoother threading, particularly in through-holes. As such, these taps are ideal for high-speed threading where chip clearance is critical.
5. Spiral Flute Tap
Spiral flute taps have helical flutes that pull chips out of the hole, making them ideal for blind holes and materials that produce short chips. This design aids in smoother threading by improving chip clearance, especially in soft metals. Though their cutting edge may be slightly weaker than hand taps, they excel at preventing clogging and providing clean threads.
6. Machine Tap
Machine taps automate the threading process using machines like CNC or tap drill machines, reducing manual labor and minimizing the risk of damage to the workpiece and tap. Built for durability, these taps handle hard materials and can thread both blind and through holes where other taps may struggle. To enhance wear resistance and extend lifespan, manufacturers often coat machine taps with titanium nitride.
7. Thread-Forming Tap
Thread-forming taps, also known as fluteless taps, shape threads through a cold-forming process instead of cutting. This process displaces metal rather than generating chips, eliminating the need for chip removal. As a result, these taps produce stronger threads that are less likely to break. Contrary to common belief, thread-forming taps work not only with soft materials like aluminum but also with harder materials, up to 36 HRC hardness, including many types of steel. Thus, they offer faster cutting speeds and deliver high-quality threads, making them an excellent choice for various applications.
8. Solid Carbide Tap
Solid carbide taps are highly durable and wear-resistant, making them well-suited for cutting tough materials like hardened steel. Their rigidity allows for faster cutting speeds and greater precision, though they are more brittle and require careful handling. These taps are perfect for high-performance applications where precision and material hardness are essential.
9. Pipe Tap
Pipe taps are specifically designed for cutting threads in pipes and fittings, creating tapered threads that ensure a tight, leak-proof seal. These taps are essential in plumbing, HVAC, and other applications involving materials like steel, brass, and aluminum. Due to their role in forming secure connections, pipe taps require precise threading to maintain pressure and prevent leaks, making them crucial for pressure-tight joints.
10. Gas Tap
Gas taps cut deep threads for gas fittings and pipes, ensuring a secure, leak-proof connection. Featuring 1-2 thread chamfers, they work effectively with both cylindrical and conical-shaped holes. As these taps meet the specific requirements of gas and hydraulic systems, they provide precise threading for high-pressure applications.
11. Combined Drill and Tap
A combined drill and tap tool allows users to drill and tap a hole in a single operation, saving both time and money during production. With its helical flute design, it works effectively on a variety of materials, including iron and brass. By eliminating the need to switch between drilling and tapping tools, it streamlines the process, making it ideal for high-efficiency production tasks.
12. Extension Tap
Extension taps are similar to hand taps but feature a longer shank, allowing them to reach deep or hard-to-access holes, such as those in a pulley hub. This extended reach makes them ideal for tapping in areas that standard taps cannot access, ensuring precise threading even in confined spaces.
13. Master Tap
Master taps are similar to taper taps but feature more flutes, typically 7-10, which provide additional cutting surfaces. This design allows them to cut cleaner threads in hard, strong materials. As such, master taps are extensively employed across various industries for their versatility and ability to handle demanding threading tasks with high precision.
14. Stay Bolt Tap
Stay bolt taps, typically 15-20 inches long, are crafted to cut threads for stay bolts, which secure components like machine screws or bolts. These taps match the exact diameter of the stay bolt nut and are especially useful in heavy-duty applications.
15. Interrupted Thread Tap
Interrupted thread taps feature a unique design where a tooth appears for every other thread, allowing for better chip extraction. This design helps break up chips more effectively and creates extra space for both chip clearance and lubricant flow. As a result, the tap reduces friction and improves cutting efficiency, making it ideal for machining tough or thick materials.
Summary
| Type | Hole Size/Type | Chamfer Type/Flute Design | Material | Example Applications |
| Plug | M3–M12, blind and through | 5-thread, straight | HSS (high-speed steel) | Engine blocks, molds |
| Taper | M3–M12, blind and through | 9-thread, straight | HSS | Valve bodies, hydraulic fittings |
| Bottoming | M3–M12, blind | 1.5-thread, straight | HSS | Bearing housings, blind hole components |
| Spiral Point | M3–M20, through | n/a, shallow, forward chip ejection | HSS | Thin-walled enclosures, small appliance parts |
| Spiral Flute | M3–M12, blind | n/a, helical flutes | HSS, coated HSS | Machine housings, components with blind holes |
| Machine | M3–M20, blind and through | 3–7-thread, straight | HSS, TiN-coated HSS | Automotive transmissions, CNC machined parts |
| Thread-Forming | M3–M12, through | n/a (forms threads) | HSS, carbide | Food processing equipment, medical devices |
| Solid Carbide | M3–M20, blind and through | n/a, straight/spiral | Solid carbide | Aerospace components, hardened steel parts |
| Pipe | NPT/NPTF* | n/a, straight | HSS | Plumbing fittings, gas lines |
| Gas | M3–M12, cylindrical and conical | 1–2-thread, straight | HSS | Gas regulators, high-pressure components |
| Combined Drill/Tap | M3–M10, through | n/a, helical | HSS, carbide | Electrical boxes, chassis components |
| Extension | M5–M16, blind and hard-to-reach | n/a, long shank, straight | HSS | Deep hole components, complex assemblies |
| Master | M8–M24, blind and through | 7–10-thread, straight or spiral | HSS | Calibration tools, inspection gauges |
| Interrupted Thread | M5–M16, blind and through | n/a, alternating teeth, straight/spiral | HSS | Deep threaded components requiring good chip clearance |
Thread Tap Size Chart
A thread tap size chart provides the necessary dimensions for selecting the right tap for a specific threading job. Below is the drill and tap size chart.
How to Choose the Right Tap Type?
Choosing the right tap type depends on several factors. Here are some key points to consider:
- Material: Softer materials like aluminum are best tapped with standard taps, while harder materials like steel may require taps made from tougher materials, such as carbide or high-speed steel.
- Hole Type: For blind holes, bottoming or plug taps are ideal, as they can reach the bottom without leaving uncut threads. For through holes, taper or spiral point taps are suitable for their ability to clear chips efficiently.
- Thread Form: If you need to form threads without cutting, choose thread-forming taps. However, consider cutting taps like spiral flutes or machine taps for cutting threads.
- Precision and Application: For high-precision work, select taps with more flutes, like master taps. In contrast, for larger-scale production, combined drill and tap tools can speed up the process.
Taps Vs. Dies
Taps and dies are both essential tools for creating threads, but they serve different purposes and are used in distinct situations.
- Purpose: Taps create internal threads in holes, while dies form external threads on rods.
- Design: Taps feature flutes for material removal during threading, while dies have cutting edges to thread the rod’s surface.
- Applications: The former is commonly used for threaded holes in manufacturing, automotive, and construction, whereas the latter is essential for making bolts, nuts, and screws.
- Types: Taps come in straight, spiral point, and spiral flute designs, and dies can be split or solid.
- Material: Both tools are typically made from high-speed steel or carbide for durability.
- Operation: Taps are rotated into holes to cut threads, while dies are turned around rods to shape external threads.
Thread Machining Services at Runsom Precision
At Runsom Precision, we provide high-precision thread machining services for a variety of industries, including automotive, aerospace, and medical. Our capabilities include tapping, thread milling, and thread rolling, using advanced CNC technology to deliver accurate, custom threads in a range of materials such as aluminum, stainless steel, and titanium. With a focus on quality, we ensure every threaded component meets strict standards. Whether for internal or external threads, we guarantee superior performance and precision in every project. Please feel free to contact us or ask for an instant quote.