Tools for threading and tapping with lathes
In lathe machining, threading and tapping are common threading methods, used to produce external and internal threads, respectively. The tools used directly impact the quality and efficiency of thread processing. Threading tools primarily consist of dies and die holders, while tapping tools include taps and tap chucks. These tools each have specific requirements regarding their structure, materials, and usage. Understanding and mastering the characteristics of these tools and their proper use is key to ensuring high-quality thread processing on a lathe.
The die used for threading is a standard threading tool. Its outer ring shape features an inner hole with a thread profile matching the specifications of the thread being machined. It also has three to four chip flutes around its circumference to remove chips generated during the cutting process. Dies are categorized by structure as either integral or adjustable. Integral dies are simple to manufacture and cost-effective, but the thread size cannot be adjusted, making them suitable for batch processing of threads of the same specification. Adjustable dies feature an axial groove on their outer circumference and an adjustment screw that allows fine-tuning of the die’s thread size. These dies are suitable for applications requiring high precision or requiring adjustment of thread clearance. Dies are typically made of high-speed steel or carbide. High-speed steel dies are suitable for processing threads in softer materials such as mild steel and aluminum alloys, offering high sharpness and wear resistance. Carbide dies are suitable for processing threads in harder materials such as high-carbon steel and stainless steel, and can withstand greater cutting forces.
The die holder is a tool used to install and clamp the die. Its function is to fix the die on the lathe and transmit torque to achieve threading. The structure of the die holder usually consists of a clamping body, fastening screws and a handle. The clamping body is provided with a mounting hole that matches the shape of the die. After the die is placed in the mounting hole, it is clamped by the fastening screws. The handles are installed on both sides of the clamping body to facilitate the operator to rotate the die holder for threading. The specifications of the die holder should match the size of the die. Different specifications of die require corresponding die holders to ensure the stability of the installation and the safety of the processing. When using the die holder, make sure that the axis of the die coincides with the axis of the lathe spindle, otherwise the processed thread will be skewed, affecting the fitting performance of the thread.
Tapping taps are the primary tool for machining internal threads. They are cylindrical in shape, with a thread profile matching the thread being machined. They also feature three to four axially oriented chip flutes to collect and remove chips. Taps are categorized by their intended use as either hand or machine taps. Hand taps typically consist of two tapers, one with a head and one with a second taper. The head taper has a longer cutting section, which carries a greater cutting load, and is used for initial thread production. The second taper has a shorter cutting section, which is used for finishing and improving thread accuracy. Machine taps are typically single tapers and are suitable for automated tapping on lathes. Tap materials are similar to die taps. High-speed steel taps are suitable for machining internal threads in softer materials, while carbide taps are suitable for machining internal threads in harder materials. Furthermore, there are spiral-fluted taps with spiral-shaped chip flutes, suitable for machining blind hole threads. These flutes evacuate chips from the opening, preventing them from clogging the bottom.
A tap chuck is a tool used to mount and hold taps on a lathe. Its function is to ensure smooth torque transmission during the tapping process and provide a certain degree of cushioning and protection, preventing the tap from breaking due to excessive force. A tap chuck typically consists of a chuck body, a spring, and an adjustment nut. The chuck body has a tap mounting hole, and the adjustment nut allows the clamping force to be adjusted to accommodate taps of varying sizes. The spring provides a certain degree of elasticity during tapping. When excessive cutting forces occur, the spring deforms, reducing the impact force on the tap and protecting it. When using a tap chuck, the appropriate chuck should be selected based on the tap’s specifications. Ensure that the tap’s axis aligns with the lathe spindle’s axis to ensure the internal thread axis is perpendicular to the workpiece end face. Additionally, a suitable cutting fluid should be used during tapping to reduce cutting temperature, minimize tap wear, and improve thread surface quality.
During lathe threading and tapping, proper tool maintenance and care are crucial to extending their lifespan and ensuring machining quality. Dies and taps should be cleaned promptly after use to remove chips and oil from the surface, then coated with anti-rust oil to prevent rust. Worn dies and taps should be promptly sharpened, maintaining their original geometric parameters, such as the thread angle, rake angle, and relief angle, to ensure thread machining accuracy. Die holders and tap chucks should also be regularly inspected to ensure their clamping mechanism is flexible and secure, free of looseness or damage. Tool storage also requires proper care. Dies, taps, die holders, and tap chucks should be stored separately in a dedicated toolbox to avoid collisions and damage. Proper use and maintenance of threading and tapping tools not only improves threading quality and efficiency, but also reduces production costs, providing a strong foundation for machining operations.
