Threading Taps Explained: Types, Uses & Selection Guide

Threading taps are cutting tools used to form threads on the holes that have been drilled or bored by drilling machines. A suitable tap guarantees that the created holes will have good threads for screws and bolts to engage with smoothly. They are applied in different areas, including the manufacturing industry, repair shops, and even personal projects.

There is a wide variety of taps, so it is necessary to understand which one is appropriate for which task.

What is a Threading Tap?

A threading tap is a cutting tool that forms threads on holes bored by drilling machines. It has specialized cutting edges that remove unwanted material and guide the tool to create threads on the newly bored hole.

Threading taps can be applied almost in all materials, including

steel, stainless steel, aluminum, brass, copper, cast iron, plastics, and composites. However, some are designed for specific applications and material types. They can also be grouped according to their usage, which includes manual and machine screw taps.

Types of Threading Taps

There are different types of threading taps, each with a unique application. Understanding their purposes facilitates the threading process and prevents damage to these tools.

Taper Tap

Taper taps have a gradually tapered lead and a few threaded points at the tip. They are typically used for starting threads manually or with machines. They are suitable for rough work.

The taper taps are appropriate for

making initial threading, hand tapping, and even improving the alignment of existing threads.

Plug Tap

Plug taps have the most common design among all threading taps. The lead diameter tapers for only a short distance at the tip; thus, they are easy to use. These taps are suitable for general-purpose threading.

Their major applications include

the maintenance field, machine threading, and even in the manufacturing industry. Most people regard these taps as the best multipurpose tools for threading machines.

Bottoming Tap

Bottoming taps rarely have a taper, which allows them to cut deeper inside the workpiece. Consequently, they are perfect for cutting threads in blind holes. They usually have the least taper, and therefore, they should not be used for initial threading.

This type of tap is appropriate for

cutting threads in blind holes to their deepest point and finishing the threads cut by other taps. When using a bottoming tap, the engagement of the tap’s threads should begin immediately.

Spiral Point Tap

Spiral point taps, alternatively referred to as gun taps, have a spiral point that facilitates the forward movement of chips. As a result, they provide faster cutting speeds, have an extended tool life, and are best for use when machining through holes.

These taps have several advantages over other tools, including

rapid metal removal, reduced chip clogging, excellent performance in through holes, and a longer tool life. They are commonly used in automated machining and production.

Spiral Flute Tap

Spiral flute taps are characterized by the absence of a spiral point. Unlike the spiral point taps, the spiral flute taps elevate the chips away from the tap body.

The major applications of spiral flute taps include

machining blind holes, threading deep holes, machining soft metals, and even CNC machining. As a result, the removal of chips, especially from blind holes is greatly facilitated. In addition, the chips do not form a wad that would prevent the spiral flute from removing them.

Form Tap

Form taps are designed to shape the threads by displacing the unwanted material. They facilitate the formation of threads without removing material via shearing.

Their benefits include

eliminating chips formation, maximizing the thread’s integrity and strength, increased tool life, and even enhanced surface finish. On the downside, they can only be used to machine ductile materials such as aluminum, copper, and steel.

Types of Threads That Can Be Cut Using Threading Taps

It is possible to determine the type of tap that can be used based on the standard thread dimensions and types. Some of the various standard thread types include metric, unified coarse (UNC), unified fine (UNF), British standard pipe (BSP), national pipe thread (NPT), acme, and trapezoidal threads. It is important to choose the best threading tap based on the workpiece’s requirements and the machine tools likely to be used.

Materials Used to Make Threading Taps

Threading taps are manufactured using different materials depending on their intended use. However, the most common types include high-speed steel (HSS) and carbide.

HSS Taps

High-speed steel taps are ideal for cutting threads manually due to their moderate price, excellent workability, and higher durability. Although they can also be applied when using machines, they are not the preferred option. This is because their performance is not adequate when cutting certain materials, including cast iron, austenitic stainless steel, and other difficult-to-machine materials.

However, high-speed steel taps can successfully cut through most standard materials, including low carbon steels, aluminum, brass, and plastics. Cobalt high-speed steel taps are ideal for threading austenitic stainless steel, high-strength steel, hard alloys, and even powder metal.

Powder Metal Taps

These types of taps are a combination of high-toughness powder metallurgy steel and high-wear-resistant powder metallurgy steel. They offer an improved balance between durability and toughness, which makes them suitable for high-volume manufacturing, CNC machining, and even tapping abrasive materials.

Carbide Taps

Carbide taps are best for high-performance machining applications. They provide a high level of hardness, which guarantees better performance when cutting extremely tough materials. They are commonly used in machining and manufacturing industries due to their long tool life. However, due to their brittleness, carbide tapping necessitates the use of a stiff machine tool spindle.

Factors to Consider When Selecting Threading Taps

Several aspects should be considered when choosing the best threading tap. This includes the type of material being machined, the hole’s dimensions and design, the volume of production, and even lubrication.

Material Being Machined

When tapping different materials, it is essential to choose the most appropriate type of tap. For example, spiral flute or form taps should be used when machining aluminum. For stainless steel, cobalt taps that have been coated appropriately should suffice. On the other hand, cast iron is usually tapped using straight flute taps.

Through Hole or Blind Hole

When machining blind holes, spiral flute taps should be used because they lift the chips away from the hole’s base, preventing them from re-engaging with the tap. Conversely, spiral point taps should be used when machining through holes since they allow the chips to be removed from the far end of the hole.

Size and Pitch

It is crucial to choose the correct size and pitch according to the fastener’s specifications. Failure to do so may result in the produced threads being non-functional.

Volume of Production

When deciding the most economical tap, it is essential to consider the likely production rate. Hand tapping is convenient for occasional maintenance and repair tasks. However, for production machining, it is advisable to use a machine tap. This is because they guarantee a high production rate, better control, and minimize the need for hand tapping.

Lubrication When Machining Taps

Lubrication reduces friction while tapping, thus facilitating a better surface finish. In addition, it prolongs a tap’s life while minimizing the possibility of thread stripping or breakage. Different materials respond differently to various lubricants.

Common Applications of Threading Taps

Threading taps have a wide range of applications, making them one of the most useful tools in the manufacturing industry. Some of the common applications of threading taps include

automotive, aircraft and heavy equipment manufacturing, hydraulic systems, plumbing, electrical enclosures, industrial machinery, medical equipment, and even repair and maintenance. In short, whenever there is a need to produce accurate threads on a bored hole or material, a threading tap is likely to be involved.

Ways of Increasing the Longevity of the Threading Taps

The long-lasting nature of a tapping tool is significantly determined by how good the user is when using it. Therefore, to maximize the utility of these tools, it is advisable to follow certain practices when tapping. These include always using the right size hole, maintaining the proper alignment of the tap within the hole, and using the recommended cutting fluid.

Moreover, it is always important to clean the chips from the workpiece, especially when hand-tapping. This will ensure that no binding occurs. Other helpful measures include avoiding unnecessary high-speed tapping and replacing a threading tap when it has been worn out significantly. In addition, tapping should always be done on stable fixtures to avoid damaging the workpiece or the tap itself. Finally, regular inspection of the tap can help detect a number of problems early on.

Conclusion

From the above discussion, it is evident that there is great variety in threading taps. As such, it is paramount to identify the most appropriate type according to the application, required thread type, and even the material of the workpiece. By doing so, one can maximize the tool’s efficiency while minimizing costs.