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The Cause and Prevention of Manually Tapped Broken
Manual tapping is one of the most commonly used machining processes. In manual tapping, tapping tools are manually operated to cut threads into an existing hole drilled into the material being machined. Manual tapping may be a more economical process than other tapping methods, but it is time-consuming, requires more experience and skill from the operator, and can produce poor results if the operator is not careful. Tapping breakage is one of the common problems in manual tapping, which affects the quality and productivity of the machining process. To ensure the quality and efficient use of manual tapping, we must first understand the cause and prevention of this problem.
The causes of tapping breakage can be divided into two main categories: excessive stresses and tool defects. The maximum stress in manual tapping is caused by cutting force, which depends on chip thickness, cutting speed and shape, etc. If the cutting force is too large, the thread will be broken. Excessive cutting force is usually caused by improper selection of taps (e.g. over-speed, unsuitable tap specification, inferior tap material) or tools (e.g. incorrect tool geometry, wear or defects).
On the other hand, the tool defects can cause the taps to break. The common defects include too thin tap flutes, poor tap tip design, broken tap edges and chipped tap corners resulting from incorrect tap grinding. Similarly, tap breakage could also be caused by insufficient strength of taps or resistance to wear, leading to premature tap failure.
To prevent tapping breakage, proper selection and inspection of taps are essential. The selection should take into account the material and hole specification, expected tool life and required surface finish. The wear resistance and strength of the taps should also be taken into account. In addition, all taps should be inspected before use, and any defect should be repaired or replaced immediately. Proper tapping operations should be followed, i.e. a suitable location and orientation of the tap should be determined, and a compatible cutting speed and feed should be used. It is also recommended to reduce cutting force, for example, by limiting penetration depth of the tap. Finally, frequent tool replacement and correct tap grinding technology are also needed for tapping breakage control.
In conclusion, tapping breakage is a common problem in manual tapping. It is caused by either excessive cutting force or tool defects, and can be prevented by proper selection and inspection of taps, following proper tapping operations and frequent tool replacement and correct tap grinding technology. With these measures, manual tapping can be a reliable and economical machining process.
