When working in modern manufacturing, threading holes quickly and accurately is a significant challenge. Manual tapping requires time and can lead to mistakes. Teams want to boost speed, repeat errors, and get tight fits for every screw. Companies look for ways to save labor, improve product quality, and meet strict requirements. CNC tapping solves these problems.
CNC tapping can seem complex at first, but the basics are easy to learn. Want to know how this process works and why so many shops rely on it? Keep reading—this guide covers all you need to know about CNC tapping.
What Is CNC Tapping?
CNC tapping is an automated process that creates internal threads in holes using a computer-controlled machine. CNC tapping utilizes a specialized tool known as a tap. The tap spins and moves into the hole at the right speed. The machine follows a set program, so every thread has the same depth and pitch.
It works on various materials, including steel, aluminum, and plastics. It can be used for internal threads on any part where screws or bolts are needed. CNC tapping is a common feature of many machining centers and can be performed either vertically or horizontally.
How Does CNC Tapping Work?
CNC tapping uses a tap and a CNC machine. The process begins with the operator setting up the part and selecting the correct tool. The machine reads a program that tells it where to make each hole.
The spindle spins the tap at a set speed. The machine moves the tap straight into the pre-drilled hole. As the tap turns, it cuts threads into the sides of the hole. The machine controls the speed, feed, and depth, so every thread is uniform.
After finishing one hole, the machine pulls the tap out and moves to the next spot. This process repeats until all holes are done. The machine can use different tap sizes if the program calls for them.
CNC tapping can be done with cutting taps or forming taps. The main difference is that cutting taps remove material while forming taps push the metal into shape to create the thread.
Types of Taps for CNC Machining
Choosing the right tap depends on the type of hole, material, and desired thread quality. Each tap is made for a specific job. Here’s a breakdown of the most common types used in CNC machining.
Through Hole Tapping
Through holes go all the way through the material. Chips can escape out the bottom. This makes them easier to tap. You can use higher speeds and reduce the risk of chip buildup. Spiral point taps work well here because they push chips forward and out.
Blind Hole Tapping
Blind holes stop before reaching the other side. Chips have nowhere to go. This means they can clog the hole or break the tap. For blind holes, spiral flute taps are the best option. They pull chips up and out of the hole. You also need to control the depth precisely.
Straight Flute Taps
Straight flute taps are the most basic type of tap. They cut threads by slicing through the material. These taps are best suited for short runs and materials that produce small chips, such as cast iron. They’re not particularly adept at clearing chips, so they’re not ideal for blind holes.
Spiral Flute Taps
Spiral flute taps are designed to pull chips back up. They’re used primarily for blind holes. The spiral design helps prevent chip clogging. They work well in soft metals, such as aluminum or brass. They also reduce the chance of tap breakage.
Spiral Point Taps
Spiral point taps are also called “gun taps.” They push chips forward, away from the tap. This makes them ideal for through holes. They can run faster than other taps. They also last longer in high-production settings.
Forming Taps
Forming taps don’t cut material. Instead, they push the material to form threads. There are no chips created. This makes them suitable for materials like aluminum or soft steel. The threads are usually stronger, but forming taps needs a larger pilot hole. Lubrication is crucial in reducing heat and friction.
Key Parameters for Successful CNC Tapping
CNC tapping needs careful setup. The correct settings keep threads clean, avoid tool breakage, and help taps last longer.
Speed and Feed Rates
Tapping speed is measured in revolutions per minute (RPM). Too fast, and the tap may break. Too slow, and you lose time. The right speed depends on the material and tap type. Harder materials need slower speeds. Softer materials can run faster.
The feed rate is tied to the thread pitch. For tapping, the feed must match the pitch exactly. If it doesn’t, the tap can either strip the threads or snap. Most CNC machines handle this with a tapping cycle that locks feed to spindle speed.
Depth of Cut
Depth refers to how far the tap goes into the hole. For blind holes, this must be controlled with great care. If the tap hits the bottom too hard, it can chip or break. Always allow clearance beyond the thread length. Through holes are easier but still need proper programming to avoid cutting too deep.
Coolant and Lubrication
Coolant helps reduce heat. Lubrication helps lower friction. Both are needed to protect the tap and improve thread quality. Use cutting oil for steel or stainless steel. Use water-based coolant for aluminum. For forming taps, always apply generous lubrication to avoid overheating. Good fluid flow also helps with chip removal in blind holes.
Common Materials for CNC Tapping
Different materials behave in various ways during tapping. Choosing the right tap and settings depends heavily on the material you’re working with.
Metals
Aluminum is soft and easy to tap. It allows fast speeds and light pressure. Use sharp taps and keep the flutes clear. Spiral point or forming taps work well with aluminum.
Steel comes in many grades. Low-carbon steel taps easily. High-carbon and alloy steels need slower speeds and more cutting force. Use cutting taps with coatings, such as TiN, for longer tool life.
Titanium is tricky and sticky. It generates heat fast. Use slow speeds, high lubricity coolant, and strong, coated taps. Spiral flute taps help manage chip removal. Tapping titanium often requires rigid setups to prevent tool deflection.
Plastics and Composites
Soft plastics, such as nylon or ABS, are easy to tap. Avoid overheating, which can cause melting. Use high-speed settings and sharp taps. Clear chips often.
Composites like fiberglass or carbon fiber are more abrasive. They wear down taps quickly. Use taps with special coatings. For brittle materials, reduce tapping force to avoid cracking or delamination. In many cases, thread-forming inserts are used instead of direct tapping.
Advantages of CNC Tapping
CNC tapping offers many benefits for modern production. It boosts both part quality and overall shop performance.
Precision
CNC machines control every movement of the tap. This results in an exact thread size, depth, and alignment. You get consistent threads even on tight-tolerance parts. There’s less risk of cross-threading or oversized holes.
Efficiency
CNC tapping runs fast. Once programmed, the machine taps hole after hole without stopping. Chip handling, tool motion, and depth are all optimized for enhanced performance. This reduces cycle time and minimizes manual work.
Versatility
CNC tapping is compatible with a wide range of materials. It handles a wide range of materials, including soft metals, hardened steel, plastics, and composites. You can tap blind or through holes, big or small, with the right tool and settings.
Repeatability
Every part gets the same result. The tap enters the same spot, cuts to the same depth, and exits cleanly. This repeatability helps with quality control. It also lowers scrap rates and reduces the need for rework.
Challenges in CNC Tapping
CNC tapping is efficient, but problems still happen. Knowing the common issues helps you prevent costly downtime or scrap.
Tap Breakage and Wear
Tap breakage often comes from using the wrong speed or feed. It can also happen if the hole is too small. Hard or sticky materials, such as stainless steel and titanium, increase stress on the tap. Taps also wear out over time. Dull tools cut poorly and are more likely to snap.
To reduce breakage, use the right tool for the job. Keep the tap sharp, and apply the correct lubricant. Rigid setups help prevent vibration and misalignment.
Thread Quality Issues
Poor alignment, dull taps, or incorrect feed rates can lead to bad threads. Threads may be too tight, too loose, or uneven. In blind holes, a worn-out tap may not cut the full thread depth.
Use a quality tap and check the hole size before cutting. Make sure the machine settings match the thread pitch. Also, inspect the finished threads regularly with gauges to catch problems early.
Chip Evacuation Problems
Chips that don’t clear can clog the flutes and break the tap. This is common in blind holes or soft materials that make long chips.
Use spiral flute taps for blind holes and spiral point taps for through holes. Keep coolant flowing to help push or pull chips out. In tough materials, reduce the feed rate slightly to give chips more time to exit.
Conclusion
CNC tapping is a reliable method for creating precise, repeatable threads in various materials. It works well for both through and blind holes. With the right tap, proper setup, and reasonable chip control, you can achieve high thread quality and reduce tool wear. It saves time, improves consistency, and supports high-volume production across many industries.
Need help with tapping solutions for your custom parts? Contact us today to discuss your project—we’re ready to support your machining needs with fast, professional service.
Hey, I'm Kevin Lee
For the past 10 years, I’ve been immersed in various forms of sheet metal fabrication, sharing cool insights here from my experiences across diverse workshops.
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Kevin Lee
I have over ten years of professional experience in sheet metal fabrication, specializing in laser cutting, bending, welding, and surface treatment techniques. As the Technical Director at Shengen, I am committed to solving complex manufacturing challenges and driving innovation and quality in each project.
