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简体中文 Taps are core tools for machining internal threads in mechanical processing. Made of high-hardness steel or cemented carbide, a tap features cutting edges and guide structures at the front to produce precise standard internal threads. Based on different thread forming principles, industrial taps are mainly divided into two types: cutting taps and extrusion taps. Though applied for the same purpose, they differ greatly in forming principle, tool shape, thread structure, applicable materials and processing characteristics. In actual production, reasonable selection of taps and processing methods according to workpiece materials, thread specifications and assembly requirements is essential to ensure stable thread quality and production efficiency.
Cutting Tap
Forming Principle
The cutting tap adopts the material removal forming method. During processing, the cutting edges scrape off excess metal from the workpiece to form chips, and the reserved hole wall forms standard thread profiles. Cutting taps are designed with special chip flutes to avoid chip accumulation, tool jamming and tap breakage, ensuring smooth machining.
Applicable Materials
Cutting taps have strong material adaptability. They can machine most metal materials, including stainless steel and high-hardness steel. They are also suitable for thread processing of magnesium alloy die castings, making them the most versatile thread machining tools.
Application Scope
Cutting taps can produce high-quality standard threads on hard and deformation-resistant materials. However, deep chip flutes reduce the overall tool strength. For aluminum alloy die castings, cutting taps are not recommended for small thread holes due to easy chip accumulation and low yield rate. They are only suitable for large threads of M12 and above.
Extrusion Tap
Forming Principle
The extrusion tap works through metal plastic deformation. Without cutting edges and chip flutes, it removes no workpiece material during operation. Under extrusion pressure, the metal around the bottom hole flows and fills the tooth gaps to form complete thread profiles without generating any metal chips.
Applicable Materials
Extrusion taps only apply to ductile and soft materials with good plasticity, such as aluminum, copper, brass and low-carbon steel. They are not suitable for brittle materials. Brittle materials cannot achieve uniform plastic flow and are prone to cracking and thread chipping during extrusion, leading to defective threads.
Processing Characteristics
Chip-free processing, ideal for blind holes and small holes
Extrusion tapping produces no chips, which simplifies processing and reduces chip cleaning time and production cost. It solves the difficulty of chip removal for small thread holes and is widely used for machining holes below M10.
Cold hardening improves thread structural strength
The plastic extrusion process causes cold hardening on the thread surface. This effect improves the surface hardness and compactness of the thread base material, making extruded threads stronger, more wear-resistant and longer-lasting than cut threads.
Core Differences Between Cutting and Extrusion Threads
Surface Finish
Threads processed by extrusion taps have a compact and smooth surface with no tool marks or burrs, meeting high precision requirements without secondary finishing. In comparison, cut threads have obvious tool marks and lower surface finish.
Pitch Diameter Accuracy
Extruded threads are formed by plastic shaping, with full and uniform tooth profiles and stable pitch diameter. Cut threads are easily affected by cutting allowance and chip discharge, resulting in larger dimensional fluctuation.
Tool Service Life and Machining Efficiency
Extrusion taps have no cutting edge wear and minimal abrasion during operation, so their service life is much longer than cutting taps. They support high-speed automatic machining, effectively improving efficiency and reducing tool replacement costs and downtime.
Tool Breakage Resistance
Without deep chip flutes, extrusion taps have a larger core diameter and more solid structure. Free from chip interference, they are not easy to break. Nevertheless, extrusion tapping requires higher torque due to plastic deformation, which demands better machine stability.
Key Operation Notes for Taps
1. Extrusion tapping requires 2 to 3 times more torque than cutting tapping. It needs equipment with sufficient power, stable workpiece clamping, reliable machine tools and high-strength tool holders to avoid processing failures.
2. Material selection rules must be followed strictly. Extrusion taps are only used for ductile materials such as aluminum, copper and low-carbon steel. Brittle materials including cast iron and normal-temperature magnesium alloy must adopt cutting 도청.
3. Bottom hole tolerance must be strictly controlled. The allowable error for extrusion tapping is only 5% of the thread pitch. An oversized bottom hole causes incomplete threads and large minor diameter; an undersized bottom hole leads to sharp tooth tips and small minor diameter, resulting in assembly errors.
4. Extruded thread holes tend to produce burrs on the end face. Chamfering is required after processing to remove burrs and ensure flat assembly contact.
5. Appropriate cutting fluid should be used to reduce material adhesion and ensure stable processing quality.
6. Cutting taps shall be selected with proper chip flute types according to materials and hole types to avoid chip blockage and tool breakage.
7. Extruded threads form a natural U-shaped notch at the tooth top, which is a normal plastic forming feature and does not affect thread performance. Cut threads have no such structure.
요약
There is no absolute good or bad between cutting taps and extrusion taps, and their differences lie in forming principles and application scenarios. Cutting taps feature high versatility and wide material adaptability, suitable for hard, brittle materials and large-size threads. With chip-free performance, high precision, high strength and long service life, extrusion taps are the best choice for automatic machining of small holes, blind holes and ductile soft materials. Matching proper processing methods based on material ductility, thread specifications and bottom hole accuracy is the key to stabilizing thread quality, improving production efficiency and reducing defective rates.
