Introduction
Threading with a taps is a common machining process. Threading, when done correctly, helps to increase the strength of a connection by creating the threads on two parts so they fit together. Threading can create both internal and external threads. Threading is often used to tighten two parts together, such as a nut and bolt combination. Threading can also be applied to different materials, including metals and plastics.
Unfortunately, not every threading attempt is successful. We often come across problems that occur with incorrect threading. Some common issues include tap breakage, burrs, and threading inaccuracy. In this article, we will discuss the root causes and solutions for these issues.
Tap Breakage
One of the most common issues with threading is tap breakage. This occurs when the tap is unable to withstand the forces of threading and breaks, leaving behind a mangled piece of thread. Tap breakage is typically caused by either incorrect tap selection or incorrect tap usage.
Incorrect Tap Selection
The wrong tap can lead to tap breakage. When selecting a tap, it’s important to consider the size, material, and type of the workpiece. The wrong tap will not be able to handle the forces of threading and can cause breakage. It is critical to understand the material of the workpiece and select a tap that is designed for it.
Incorrect Tap Usage
Another common cause of tap breakage is incorrect usage. It is important to ensure that the tap is properly lubricated and the feed rate is correct. Too much force can lead to the tap breaking. Additionally, it’s important to ensure that the tapping holes are clean and clear from debris. Sharp edges, burrs, and obstruction can all cause the tap to break.
Burrs
Burrs, also known as flash, is another common issue with threading. These tiny metal fragments can cause a variety of problems and even reduce part strength. Burrs are often a result of incorrect tap usage. Here are some common causes of burrs:
• Incorrect feed rate: If the feed rate is too high, it can cause burrs to form on the surface of the workpiece. The burrs form due to an excessive amount of material being removed.
• Sharp edges: When the threads are cut, sharp edges can form on the inner walls of the hole. This can cause the tap to skip, increasing the risk of burrs forming.
• Sticky chips: Sticky chips, also known as long chips, are long, stringy chips that are difficult to remove from the hole. If these are not removed, burrs can form.
Solutions
The solutions for tap breakage and burrs depend on the cause. Here are some common solutions for these problems:
• Select the correct tap: As mentioned previously, selecting the correct tap for the workpiece is critical for successful threading. This will reduce the risk of tap breakage and burrs.
• Lubricate the tap: Applying a lubricant to the tap will reduce friction and help it move more smoothly through the hole. This will reduce the risk of tap breakage and burrs.
• Increase the feed rate: Increasing the feed rate can help to clear stuck chips, reduce burr formation, and increase speed.
• Adjust the cutting parameters: Adjusting the cutting parameters such as the cutting speed, feed rate, and depth of cut can help to achieve the desired results.
• Use the correct tap drill: When drilling the hole for the tap, it is important to use the correct tap drill. This will ensure the hole is the right size for the tap and reduce the risk of tap breakage and burrs.
Threading Inaccuracy
Threading inaccuracy is another common problem with threading. This is often caused by incorrect tap selection or incorrect tap usage. Incorrect tap selection can lead to an undersized or oversized thread. Incorrect tap usage can also lead to threading inaccuracy. Here are some common issues that can cause threading inaccuracy:
• Incorrect start point: If the start point for threading is not correct, the resulting thread will not be accurate.
• Unstable workpiece or tap: If the workpiece or tap is not stable, it can lead to threading inaccuracy.
• Dirty threads: Dirty threads can lead to incorrect depth.
• Worn tap: If the tap is worn, it may not be able to create the desired threads.
Solutions
Here are some solutions to help improve threading accuracy:
• Check the start point: Make sure the start point is correct before beginning to thread.
• Check the tap: Inspect the tap to make sure it is in good condition and not worn.
• Check the tap drill: Make sure the tap drill is the correct size for the tap being used.
• Use a center drill: A center drill provides a stable start point for threading.
• Use a higher speed: Increase the speed of the tap to prevent it from skipping or stalling.
• Use a lubricant: A lubricant can help to reduce friction and improve the accuracy of the thread.
• Clean the threads: Make sure the threads are clean before each threading attempt.
Conclusion
Threading requires precision and skill. Unfortunately, threading can go wrong and it is important to understand the root causes of problems and the solutions for them. Tap breakage, burrs, and threading inaccuracy are all common issues with threading. The solutions to these problems depend on the root causes and can include selecting the correct tap, adjusting the cutting parameters, and using a lubricant. Understanding these problems and solutions will help to improve threading accuracy and reduce costly mistakes.
