Removing a Broken Drill or Tap: Tips and Tricks
Encountering a broken drill or tap in the middle of a project can be a frustrating and time-consuming setback. But…
There’s nothing quite as frustrating as a broken thread tap halting your project mid-way. This common yet exasperating issue can leave even the most seasoned machinists and DIY enthusiasts scratching their heads. But fear not—removing a broken thread tap doesn’t have to be a daunting task. Whether you’re dealing with a stubborn tap in a workshop or a machine shop, knowing the right techniques and tools can save you both time and headaches. In this guide, we’ll walk you through step-by-step methods to tackle this problem efficiently, from using specialized tools like tap extractors to manual techniques and advanced methods. Ready to reclaim your project and remove that broken tap with confidence? Let’s dive in.
A broken thread tap is a common and frustrating issue in machining and manufacturing. These essential tools create threads inside holes for screws or bolts. However, taps can break due to excessive force, poor alignment, or hard materials, leaving a portion embedded in the workpiece.
Proper removal of a broken tap is crucial to salvage the workpiece, avoid costly rework, and minimize downtime. Tap breakage can result from material hardness, incorrect tap selection, inadequate lubrication, or improper technique.
There are multiple techniques for removing broken taps, each suited to different scenarios and available tools. Common methods include:
Selecting the appropriate removal method depends on the workpiece material, the tap’s size and location, and the available tools. By understanding and selecting the appropriate technique, you can efficiently remove broken taps and maintain workpiece quality.
Mastering these removal techniques will not only save time and resources but also ensure your machining projects run smoothly and successfully.
Tap extractors are tools specifically made to easily remove broken taps. They come in various sizes to match different tap diameters and feature multiple fingers that engage with the flutes of the broken tap.
For situations without advanced machinery, manual tools like cold chisels, center punches, and hammers offer a straightforward approach to removing broken taps.
Drilling and milling can be effective methods for removing broken taps, especially when precision tools are available.
For more challenging cases, specialized tools and techniques can be employed to remove broken taps.
Having the right general tools and accessories is crucial for successful tap removal.
By ensuring you have the appropriate tools and equipment, you can effectively tackle broken tap removal and maintain the integrity of your workpiece.
When part of the broken tap protrudes above the workpiece surface, you can use a cold chisel and center punch to remove it. Follow these steps:
Tap extractors are specialized tools designed for removing broken taps. To use a tap extractor:
This method is efficient but may not work if the tap is deeply embedded or if the flutes are damaged.
When other methods fail, drilling and milling can be effective solutions. For example, if a tap is broken deep inside a workpiece and other methods are unsuccessful, you might choose to drill or mill it out.
To drill out a broken tap:
Milling is precise and particularly effective with rigid machines like CNC machines. Use solid carbide tools, such as ball endmills or Armor Mills, to mill out the tap, ensuring minimal damage to the workpiece.
Chemical removal involves using specific chemicals to dissolve the tap, especially in aluminum alloys. This method requires careful handling of chemicals and is less common due to potential hazards.
Electrolytic removal involves using an electric current to corrode the tap. Here’s a simplified explanation:
This method causes minimal damage to the threaded hole.
When manual or chemical methods are insufficient, welding and grinding offer alternative solutions.
TIG welding can remove a broken tap by welding a rod through the center of the tap and pulling it out. Alternatively, the entire area can be welded, ground flat, and then re-drilled and tapped.
Welding a handle or hexagonal nut to the broken section of the tap allows for reversing the tap out. This method is effective but can be challenging for smaller diameter taps.
Applying lubricating oil can help loosen the tap, making it easier to push out in the reverse direction. This straightforward method is commonly used in machine shops.
Electric pulse and EDM (Electrical Discharge Machining) methods are highly effective for deeply embedded taps. These techniques allow for reaming and adding a threaded wire sleeve afterward, ensuring the integrity of the threaded hole.
Before using an extractor to remove a broken tap, it’s crucial to prepare the workpiece thoroughly. Clean the area around the broken tap to remove any chips and debris. This ensures that the extractor can fit properly into the flutes of the broken tap and increases the chances of successful removal.
Insert the extractor fingers into the flutes of the broken tap, ensuring they align correctly. Push the fingers gently but firmly into position, as the depth of the fingers in the flutes is crucial for effective removal.
Once the extractor fingers are in place, push the holder piece of the extractor downward until it touches the broken tap. Then, slide the sleeve down until it touches the workpiece. This ensures that the extractor is securely positioned and ready for the next step.
Attach a tap wrench to the square end of the holder. Twist the wrench back and forth a few times to loosen the broken tap. After loosening, continue to turn the wrench in the direction opposite to the thread direction to back out the broken tap.
Tap extractors, like those from Walton, fit different types of taps, including machine screw, hand, pipe, and STI taps. They come in various flute styles, so always choose the right size and style for the specific tap to ensure the best results. With the correct tools and careful technique, you can successfully remove broken taps.
Using a cold chisel and center punch is an effective manual technique for removing broken taps, especially when part of the broken tap is protruding above the surface of the workpiece.
A thread crown is a specialized tool designed to remove broken taps by engaging the tap’s grooves and unscrewing it.
Drilling out a broken tap can be an effective manual technique, especially when precision tools are available. This type of drill can help unscrew the tap as you drill.
Using lubricating oil can significantly aid in the manual removal process by reducing friction and loosening the broken tap.
Grinding and milling are useful techniques for removing broken taps, especially when other methods fail. First, use a grinder to flatten the surface of the broken tap. Then, use a drill to gradually increase the width of the hole around the tap. This process may need to be repeated until the tap is completely removed. Finally, use needle-nose pliers or another suitable tool to pick out any remaining fragments.
Welding can be an effective method for creating a handle or a hex nut on the broken tap for easier removal.
Each of these manual techniques offers a practical solution for removing broken taps, depending on the specific circumstances and available tools.
TIG welding is a highly effective method for removing broken taps, especially when traditional methods fail. This technique uses a type of welding that employs a tungsten electrode and inert gas to build up material on the broken tap, creating a surface that can be gripped and removed.
Building a Head: Carefully add layers of weld material to the broken tap to create a small protrusion that can be gripped.
Using Vise Grips or a Nut: Once the head is built, use vise grips or weld a nut onto it to twist and remove the tap.
Material and Equipment: Utilize a fine-point tungsten electrode and suitable filler metal, such as stainless safety wire (.030″). This method works well on various materials, including aluminum, steel, and stainless steel.
Caution: Be mindful of the heat generated during welding, as it can cause the hardened tap to fracture and come out in pieces. This method is particularly effective if the tap is not cracked along its centerline.
Electrical Discharge Machining (EDM) is another advanced method known for its precision and effectiveness in removing broken taps. This technique uses electrical discharges to erode the material around the tap, allowing for its removal without damaging the workpiece.
Setting Up the EDM Machine: Use an EDM machine, such as a ram EDM or sinker EDM. Ensure the workpiece is properly grounded and the electrode is accurately positioned.
Burning Out the Tap: Insert a copper or graphite electrode into the EDM machine. The electrode erodes the tap with precision, disintegrating it and leaving only the cutting edges stuck in the threads, which can then be manually removed.
Preserving Threads: EDM is highly effective in preserving the threads of the workpiece. The process can remove the steel part of the tap while leaving the aluminum or other material threads intact.
Post-Removal: After burning out the tap, inspect the hole and remove any remaining tap material using a screw or other tools to clear the threads.
Limitations: While EDM is reliable, it can be time-consuming and requires specific equipment. Despite this, it remains one of the most dependable methods for removing broken taps without damaging the surrounding material.
EDM machines can use various electrodes, including portable options, to remove broken taps efficiently. These methods are particularly useful for smaller workpieces but can be limited by the axial orientation of the threaded hole.
Proper lubrication is essential to reduce friction and prevent tap breakage. Using an adequate amount of cutting fluid minimizes the heat generated during the tapping process and helps remove chips more effectively. While special oils made for cutting are available, common alternatives like sunflower oil can be cost-effective and sufficient for many applications. Regular application of cutting fluid ensures smooth operation and prolongs the life of the tap.
Choosing the appropriate hole size is crucial for preventing tap breakage. The hole size should accommodate the tap without excessive force. Often, the hole size suggested on tap packaging might not work well for every material. Adjusting the drill size to achieve the desired thread percentage can significantly reduce the likelihood of breakage. A proper balance between the hole size and tap ensures smooth threading and less stress on the tap.
Adopting an intermittent cutting technique helps prevent chip buildup and reduces the risk of tap breakage. Try turning the tap back slightly after every full rotation to see how it breaks chips effectively. This method, known as "backing off," facilitates chip clearance and reduces the amount of force required, thus protecting the tap from excessive stress.
Ensuring the tap is correctly aligned with the hole is critical for successful threading. Misalignment can lead to uneven force distribution and increase the risk of breakage. To keep the tap straight, use alignment tools like a sliding guide or spring-loaded plunger. Proper alignment minimizes lateral forces and keeps the tap centered, enhancing the threading process’s accuracy and efficiency.
Keeping taps in good condition is essential for preventing breakage. Regularly inspect taps for wear and sharpness, as a dull tap requires more force and is more prone to breaking. Sharpening or replacing dull taps ensures they cut efficiently and reduces the risk of breakage. Maintaining a set of sharp, well-cared-for taps extends their lifespan and improves overall performance.
Consistently applying stable and even force during the tapping process is vital. Uneven force can cause the tap to bind or break. A T-handle tap wrench helps you keep control and provide the necessary torque without overexerting the tap. A steady, controlled approach reduces the likelihood of sudden movements that could lead to breakage.
By implementing these best practices, machinists and engineers can significantly reduce the risk of tap breakage, ensuring smoother operations and longer tool life.
Below are answers to some frequently asked questions:
The most effective methods for removing a broken thread tap include using tap extractors, EDM (Electric Discharge Machining), and TIG welding. Tap extractors, designed specifically for this task, can be inserted into the flutes of the broken tap to facilitate removal. EDM is ideal for deeply embedded taps, as it precisely burns out the tap’s core. TIG welding involves building up a head on the tap, allowing for extraction with tools. Each method has its own advantages, and the choice depends on factors like the tap’s position and available tools, as discussed earlier.
To prevent a tap from breaking during threading, select the appropriate tap size and material for your workpiece, and ensure the hole size allows for optimal thread percentage. Use cutting fluid to reduce friction and prevent overheating, and reverse the tap periodically to manage chip formation. Maintain a stable force, avoid forcing the tap, and ensure the cutting chamfer extends beyond the workpiece for smooth chip ejection. Regularly check and maintain taps, consider using floating holders, and be cautious with deep holes to minimize stress and the risk of breakage.
To remove a broken thread tap, you’ll need a variety of tools depending on the method you choose. Common tools include tap extractors, which come in various sizes and require a tap wrench, cold chisels and hammers for manual removal, harder drill bits or carbide rods for drilling out the tap, and ball endmills for milling. For advanced methods, a TIG welder or an EDM machine can be used. Additional helpful tools include needle nose pliers, lubricating oil, and possibly a pneumatic drill. Each method and tool is suited to different scenarios, so select based on your specific situation.
Yes, it is possible to remove a broken tap without specialized tools, though it can be challenging and requires patience. Methods such as using lubricating oil and manual tools to reverse the tap, drilling out the tap with a harder bit, manually smashing it with a chisel and punch, or using diamond burrs or hole saws can be employed. Welding a head onto the broken tap and using chemical methods are also options. These techniques, while not always guaranteed to succeed, offer several alternatives to specialized tools, making it feasible to remove a broken tap with more readily available equipment.
To choose the right method for removing a broken thread tap, consider the material of the workpiece, the depth and location of the broken tap, the tools available, and the risk of damaging the workpiece. For example, tap extractors are effective and simple for surface breaks, while methods like EDM or milling are suitable for deeper, more challenging breaks. Drilling out or using heat can work but require caution. Assess these factors to select the most appropriate and safe method for your situation, ensuring minimal damage and effective removal, as discussed earlier.
Yes, there are several risks associated with removing a broken tap. These include potential damage to the workpiece, such as deformation or scratches, and the possibility of damaging the removal tools themselves. Misalignment during the process can exacerbate the problem, leading to further complications. Specialized methods like EDM or TIG welding require expertise and can pose additional safety risks if not handled correctly. Chemical methods can corrode the workpiece and pose exposure risks. Manual techniques also present physical risks to the operator. Therefore, it is crucial to follow best practices and consider professional assistance when necessary.
