The Evolution of Tapping Technology: Unlocking the Full Potential of Cemented Carbide Taps
In recent years, the development of machine tool control technology has led to the elimination of flexible tapping heads, enabling synchronous control of rotation and thrust, which has significantly improved the precision of tapping operations. This technological advancement has also enabled the use of hot and hydraulic tools, which can improve the rigidity of the tool and reduce radial jump errors. While the performance of high-precision high-force (TGHP) tools is slightly lower than that of hot and hydraulic tools, they are still effective in tapping applications.
In contrast, CNC machine tools cannot perform "simultaneous" tapping, which is a precise power feed that depends on the thread guide when the spindle turns. To compensate for the minor axial displacement errors in synchronous tapping machines, improvements are needed in mounted, hydraulic, and thermal-sleeved TGHP tools.
The industry standard tolerance for tap handles is relatively loose, with a range of +0.0000 to -0.0381 mm. As a result, the dimensional tolerance requirements for controlling diameter jumps are not strict. For example, according to industry standards, the diameter jump error between the handle and the thread of a 1/2" tap can reach 0.04 mm, and it is not necessary to control the diameter of the threading and the concentration of the concentricity of the inclined point handle and the handle of the tap.
To exploit the full potential of cemented carbide tool materials, Kenner has designed a new tap, the KC7542, which integrates high-performance carbide materials with a newly developed Nano-TiAlN coating for carbide forms. This design ensures effective concentricity and tightening, making it ideal for high-speed operation and minimizing the formation of long chips.
Unlike most turning, milling, and drilling tools, the tip edge of the tap is relatively low, resulting in low overall resistance and susceptibility to collapse during processing relatively easy-to-cut materials such as steel. The tip of the cemented carbide tap can also be prone to cracking, especially when processing steel with low carbon content, which can obstruct the valve chip and limit the application of cemented carbide taps to materials such as aluminum and melting.
To give a complete advantage to the TGHP tool with hot sleeves, hydraulic, or precision, the dimensional precision of the handle of this cemented carbide faucet has reached the H6 level of the German DIN 7160 standard, with a size tolerance range of +0.0000 to -0.0101 mm and a concentricity tolerance of less than 0.0030 mm.
To reduce the advanced load and prevent cracking, users had to reduce the feed rate (compared to high-speed steel drilling at high speed) when introducing the full carbide core into the hole. However, cemented carbide exercises can use faster cutting speeds, thanks to advancements in cemented carbide drilling and the design of the drilling bit.
In the development of taps, the chip load is only checked by the thread guide, thread lead number, and cutting slope, and the environmental tapping conditions make it difficult to further reduce the load acting on the edge of the tap. To avoid cracking, improving the overall carbide forest design (which enables a higher power rate) can also be applied to full carbide taps.
Table: Recommended Cutting Speed Range for Different Materials with Cemented Carbide Taps
| Part Material | Example Equipment | Diffusion Hardness | Cutting Speed (SFM) |
|---|---|---|---|
| Low Carbon Steel (C <0.25%) | 1018— | 32 HRC | 300—400 |
| Easy Steel | 12L14— | 25 HRC | 250—350 |
| Average/High Carbon Steel | 1040, 4340, H-13, D-2— | 28 HRC | 200—300 |
| Ferritic Steel, Martensitic Steel, Stainless Steel | 430, 410, 17-4PH— | 28 HRC | 150—210 |
| Ductile Steel, Forged Steel | A-47, A-536— | 32 HRC | 250—400 |
| Gray Cast Steel | 20—50— | 32 HRC | 250—400 |
(*The cutting speed listed is suitable for tapping through holes with a hole depth less than 3 times the opening)
When entering blind holes, it is essential to note that not all CNC machine tools have the same synchronous tapping capacity. The tap and pin must be slowed down and left during machining at the bottom of the blind hole, which can occur when the tap is reversed, resulting in a lateral thrust acting on the tap and causing excessive dimensions in the wire detection.
The Importance of Cutting Speed
Cutting heat is the enemy of tools. Unfortunately, at the tool/piece interface, tools often resist the reduction in high temperatures, which can shorten the life of the tool and limit the performance of the tool. To solve this problem, a wide range of tool materials has been developed, including high-speed steel and cemented carbide, both of which are commonly used. High-speed steel tools have excellent resistance and tenacity, while carbide tools are superior in terms of high hardness and red hardness (the ability to maintain hardness at high cutting temperatures).
In general, the cutting speed of the overall carbide tool can reach at least 4 times that of high-speed steel tools, and the lifespan of the tool is longer. However, compared to high-speed steel tools, cemented carbide tools have poor tenacity to fracture, which limits their application in certain fields of treatment (particularly tapping).
The Significance of Tap Stability and Synchronization
The dimensional precision of the internal thread determines the accuracy and adaptability of the assembly of the thread. When machining internal threads, the TAP is generally driven by a drilling machine or an asynchronous machine tool equipped with a flexible tapping head, which can drive the tap to turn and feed on a flow close to the wire internal thread required. These old-fashioned machines find it difficult to coordinate with feed and rotation movements during tapping, and this synergy is a necessary condition for the treatment of threads. Therefore, flexible tapping heads should be used to control the error range during tapping, which will make the valve jumps radially, limiting the improvement of the precision of the wire.
These factors lead to low machining rigidity and unequal tap loads. The successful application of cemented carbide taps depends on the tightening rigidity of the tool and the precision of power control. For most treatment methods, these treatment conditions are taken for granted. But to type, these conditions have become a reality.
In conclusion, the evolution of tapping technology has led to the development of high-precision high-force (TGHP) tools, which have significantly improved the accuracy and efficiency of tapping operations. The use of cemented carbide taps, which combine high-performance carbide materials with newly developed coatings, has enabled faster cutting speeds and longer tool life. As the demand for precision tapping continues to grow, it is essential to continue advancements in machine tool control technology, tool design, and materials science to unlock the full potential of cemented carbide taps.
