From basic hand taps for quick fixes to high-performance spiral designs for high-volume runs, knowing how different types of taps handle torque and clear out chips is essential for any successful machining project.
Types of taps for hand threading
When you’re working with a hand tap set, you typically work with three different tools: the taper, a plug, and a bottoming tap. Each serves a specific stage of the threading process to ensure accuracy and to reduce the high risk of breakage.
The taper tap features a long lead-in to help you start the thread straight. The plug tap follows to deepen those threads, while the bottoming tap is essential for blind holes. Using them in this sequence keeps the torque manageable and ensures your threads are straight and deep enough to meet the original design requirements.
Machine taps for CNC and production runs
When you move from manual work to CNC machining, tap geometry becomes a game of chip control and synchronization. Machine taps, like spiral point or spiral flute designs, are engineered to handle much higher speeds and constant pressure.
To get the best results in CNC-machining, you need to consider your tool holder. Using a rigid tapping cycle requires a synchronized holder to match the spindle speed with the feed rate perfectly. This prevents thread stripping and tool snapping. Always check the acceleration limits of your machine, as even a slight lag in the reversal ruins a high-precision part.
Spiral flute versus spiral point taps
Efficiency in tapping often comes down to how you handle chip evacuation. Spiral point taps, often called ‘gun taps,’ feature a straight flute with a specifically ground angular point. This geometry is designed to push chips forward, ahead of the cutting action, and out through the bottom of the hole.
Gun taps are the go-to choice for through-holes, as they prevent debris from clogging the flutes and causing the tool to bind. Because the flutes remain clear of chips, lubricant can reach the cutting edges more effectively, significantly extending tool life during long production runs.
On the other hand, spiral flute taps function much like a traditional drill bit, using their helical grooves to pull chips upward and out of the opening. This is vital for blind holes where chips have nowhere else to go but back toward the spindle.
When selecting these parts, pay attention to the helix angle. A higher angle, such as 45°, is typically better for soft, stringy materials like aluminum, while a lower angle provides more strength for tougher alloys. Choosing the wrong tools here is the fastest way to snap a tap and scrap a part, especially in deep-hole applications where chip packing becomes a critical risk.
Form taps for chipless internal threads
Thread forming taps, also called roll taps, work differently to traditional cutting tools. They displace material rather than removing it. Instead of cutting chips, these taps form the metal into a thread profile, which actually makes the threads stronger due to grain-flow densification.
Since no material is removed, your starting drill size is critical. It must be larger than a standard tap drill. You also need high-quality lubrication to reduce the friction generated during the process. When carried out correctly, the result is a clean, chip-free operation that is ideal for ductile materials like aluminum or soft steel.
Choosing types of taps by material and finish
To get the longest life out of your tools, match the coating of the tool to the material. TiN works for most tasks, but use a DLC coating for abrasive aluminum to stop edge wear.
Beyond coatings, always pay attention to the thread class (like 2B or 3B) to ensure the fit is just right for your assembly. Getting these surface finish details dialed in prevents galling and ensures your parts perform as intended.
Are you ready to see how precision threading can elevate your next project? Upload your CAD files to Protolabs Network for an instant quote and expert DfM feedback. You get a point-by-point document with feedback. In this way you have a suitable solution in a short amount of time.
Frequently asked questions
What is a tap used for in machining?
A tap is a cutting or forming tool used to create internal threads in a hole, allowing fasteners such as screws and bolts to be installed securely.
What are the main types of taps?
The most common types include taper taps, plug taps, bottoming taps, spiral point taps, spiral flute taps, and form taps. Each is designed for specific materials, hole types, and machining conditions.
What is the difference between a taper tap, plug tap, and bottoming tap?
A taper tap is used to start threads with minimal cutting resistance, a plug tap deepens the thread, and a bottoming tap cuts threads close to the bottom of a blind hole. These taps are often used sequentially in manual threading operations.
When should I use a spiral point tap?
Spiral point taps, also known as gun taps, are typically used for through-holes. Their geometry pushes chips forward and out of the hole, reducing the risk of chip buildup and improving tool life.
When should I use a spiral flute tap?
Spiral flute taps are best suited for blind holes as they pull chips back toward the opening, preventing chips from accumulating at the bottom of the hole.
What is a form tap?
A form tap creates threads by displacing material rather than cutting it. Because no chips are generated, form taps are ideal for ductile materials such as aluminum and mild steel.
Are form taps stronger than cutting taps?
Formed threads are often stronger than cut threads because the material grain structure is compressed and follows the thread profile. However, form tapping requires the correct hole size and adequate lubrication.
Why do taps break during machining?
Common causes include poor chip evacuation, incorrect feed rates, insufficient lubrication, misalignment, and using the wrong tap geometry for the application. Proper tool selection and process control help to minimize breakage.
What is the difference between hand taps and machine taps?
Hand taps are designed for manual threading and are often used in sets of taper, plug, and bottoming taps. Machine taps are optimized for CNC machining and production environments, where higher speeds, consistent chip control, and repeatability are required.
