Staying Ahead of Change with the A-XPF Highly Efficient and Multi-purpose Forming Tap
Keita Ono | OSG Corporation Applications Engineer (Tap Development Division)
The rise of environmental concern is increasing year by year. Along with this, a demand for environmentally friendly cutting tools has also become more prominent than ever before. OSG’s latest A-XPF high-efficiency and multi-purpose forming tap is a product that can respond to today’s evolving manufacturing needs. Compared to conventional products, the A-XPF enables higher processing efficiency, which reduces machining time. In addition, by achieving longer tool life, the number of tool changes required can be minimized. Moreover, by enabling stable and uninterrupted machining, power consumption can be reduced.
Common Tapping Troubles
Table 1 summarizes common tapping trouble consultations received at OSG’s customer service center. The number one trouble is tool breakage and chipping (26 percent); ranked at number two is dimensional error (17 percent); galling is ranked at number three (14 percent). The top three troubles combined account for 57 percent of the total.
Table 1. Top 3 tapping troubles (source: OSG Technical Consultation Division)
In all cases, the main cause of trouble is cutting chip related. During tapping, cutting chips often can become entangled with the tap as depicted in figure 1. If machining is continued under this state of condition, the chips will get caught and the tap will likely chip or break. In addition, as illustrated in figure 2, galling may occur in the internal thread.
Left: Figure 1. Chip packing – an example of cutting chip related trouble. Right: Figure 2. An example of galling.
How to Troubleshoot
To resolve chip troubles, OSG has developed the A-XPF forming tap that forms threads by plastic deformation of the work material. Therefore, no chips are generated during tapping. In other words, troubles caused by chips can be completely eliminated by leveraging the A-XPF to enable uninterrupted machining and maximize productivity.
Features of A-XPF
The first feature of the A-XPF is the adoption of a special chamfer specification, which contributes to achieving low thrust. The second feature is its special thread configuration. The rigidity of the tap is ensured by adopting a special thread geometry and a new relief shape. The third feature is the adoption of the VI coating. About 30 years after the company’s V coating, OSG has developed a new special coating uniquely engineered for taps.
1. Special Chamfer Specification
With the A-XPF’s special chamfer specification, the ridges at the tip of the tap are less likely to chip compared to the conventional style. With forming taps, when the tool enters the hole, chipping may occur on the ridge at the tip of the chamfer portion of the tap. The chipped section may lead to further chipping of the entire tap. The A-XPF incorporates a unique geometry that suppresses chipping during thrust. Figure 3 depicts a graph of the thrust measured during tapping. Compared to a conventional product, the A-XPF is able to reduce the thrust and the amplitude of the waveform. By stabilizing the thrust waveform, the tool can stably enter the workpiece.
Figure 3. Comparison of thrust during machining
2. Special Thread Configuration
When using a forming tap, the crest of the tap thread may suddenly disappear. In general, the relief shape of the forming tap tends to emphasize sharpness and is marginless. The more emphasis is placed on sharpness, the lower the rigidity of the tap thread becomes. The A-XPF adopts a new relief shape to suppress sudden chipping of the crest of the thread. Figure 4 illustrates a comparison of relief shape between a conventional product and the A-XPF. In the new relief, the shape of the cutting edge has not been altered to maintain sharpness while the back side of the thread has been thickened to ensure rigidity. The enhanced thickness is depicted in black on the right diagram in figure 4.
Figure 4. Comparison of relief shape
3. New VI Coating
The A-XPF employs a new VI coating developed exclusively for taps. The coating structure is a Cr-based composite multilayer film as illustrated in figure 5. Compared to the conventional V coating, the VI coating has improved hardness, oxidation initiation temperature, adhesion, wear resistance, and many other superior properties as shown in figure 6. Since the new VI coating can handle high-load machining, higher speed range can be achieved in comparison to conventional products.
Figure 5. Structure of the new VI coating
Figure 6. Properties of the new VI coating
Performance of the New VI Coating
Figure 7 illustrates the result of machining a work material in SCM440 (30 HRC) using a M6 x 1 A-XPF under high-speed. With the conventional V coating, wear progressed after 7,000 holes. With the new VI coating, on the other hand, 11,000 to 12,000 holes can be machined. The new VI coating has demonstrated over 30 percent longer life than the V coating.
Figure 7. Performance of the new VI coating
Figure 8 depicts the A-XPF’s superior performance under high-speed machining condition at 30 m/min in alloy steel with a hardness of 30 HRC. The A-XPF was able to complete 13,000 holes even in this machining range with stable tool life.
Figure 8. Cutting performance comparison in SCM440 (30 HRC)
Table 2 shows the standard cutting conditions for the A-XPF. Compared to conventional products, the range of cutting speeds that can be used for mild steel, high carbon steel, alloy steel, and tempered steel has expanded significantly. Suitable from low-speed machining to high-speed machining, the A-XPF is a versatile solution that can accommodate a wide range of machining environment.
Table 2. A-XPF Cutting Conditions
Productivity can be notably improved by the elimination of cutting chips. Furthermore, with the A-XPF’s unique chamfer specification and thread geometry, outstanding machining stability can be achieved. For manufacturers who are struggling with cutting chip troubles in tapping, look to the highly efficient and multi-purpose A-XPF forming tap to stay ahead of change.
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