Threading inserts serve as the essential "core teeth" of thread machining, playing a vital role across various industries, including automotive, aerospace, petrochemicals, general machinery, rail transit, and medical devices. The automotive sector represents the largest segment, accounting for approximately 35% of usage.
Different industries face distinct challenges—such as rapid tool wear, chip adhesion, high-temperature failure, and deep-hole chip clogging—due to variations in workpiece materials (like steel, titanium alloy, superalloys, and stainless steel) and operating conditions.
For instance, titanium alloys are prone to built-up edge, while superalloys require tools that can withstand cutting temperatures reaching 600–700°C. Therefore, scientific selection of threading inserts is crucial for overcoming these challenges.
Problem Analysis
-Steel machining requires a balance between high-speed cutting efficiency and long tool life to minimize production interruptions caused by frequent tool changes.
-Titanium & Aluminum Alloys: Materials like TC4 (titanium) and ADC12 (aluminum) are prone to chip adhesion, which can compromise thread surface quality.
-Industry-Specific Demands: Petrochemical pipeline joints must withstand sealing pressures exceeding 10 MPa. Aerospace applications demand extreme precision, such as 5H/5g tolerance grades. General machinery often involves diverse materials (steel, cast iron, aluminum), necessitating a careful balance between cost and performance. These combined requirements significantly increase the complexity of selecting suitable tools.
Solutions and Applications by Industry
Tailoring the insert selection to specific industry needs yields optimal results:
-Automotive Manufacturing: TiAlN-coated triangular inserts (e.g., Sandvik TNMG160408-M 6g) are ideal for machining 20CrMnTi transmission bolts. They achieve cutting speeds of 120–150 m/min, with a single insert capable of producing 3,000–4,000 parts.
-Aerospace: For TC4 titanium alloy fuselage threaded holes, CBN-based inserts with AlCrN coating (e.g., Iscar CNMG09T304-M 5H) are recommended. These maintain a thread profile error within ≤0.005 mm, achieving a qualification rate of 99.8%.
-Petrochemical Industry: Cemented carbide vertically-mounted pipe thread inserts (e.g., Kennametal VNMG250716-NPT 6g) are suitable for 35CrMo thick-walled pipelines (12–15 mm wall thickness), ensuring reliable performance at 10 MPa sealing pressure.
General Selection Methodology
A logical selection process is fundamental:
1. Define Thread Parameters: Identify the standard, thread form, and pitch.
2. Match Material & Coating: Choose the insert material and coating compatible with the workpiece.
3. Adapt to Equipment & Conditions: Consider the machine tool and specific machining environment.
4. Balance Precision & Cost: Select the optimal insert based on quality requirements and budget constraints.
Additional Practical Tips:
-Use vertically-mounted inserts for deep-hole threading to prevent chip clogging.
-For large-pitch threads (e.g., 6 mm lead screws), consider round inserts (e.g., Zhuzhou Diamond RNMG200608-Tr 7g) for their strength and durability.
Results and Benefits
-Efficiency: Batch processing of automotive rail fastener bolts can reach 120 pieces per hour. A single insert can machine 5,000–6,000 HT250 gray cast iron end caps in general machinery applications.
-Quality: Medical 316L infusion pump interfaces can be produced burr-free, complying with GMP standards. A 99.8% qualification rate is achievable for aerospace superalloy threads.
-Cost-Effectiveness: In general applications, TiN-coated inserts offer significant value, reducing costs by over 30% compared to premium high-end coatings.
Conclusion
Industry-customized selection of threading inserts effectively addresses the challenges of machining diverse materials under varying conditions, leading to substantial gains in efficiency and quality. Looking ahead, evolving demands—such as high-voltage bolts for new energy vehicles and high-temperature threads for aero-engines—will drive the development of inserts featuring ultra-fine grain substrates, composite coatings, and intelligent cutting-edge monitoring. These advancements will provide even more reliable machining support for high-end manufacturing.
