Indexable turning tools made of cemented carbide come in various structural types, including lever type, insert bolt type, wedge type, pressure type, eccentric type, pull pad type, and pressure hole type. Among the commonly used designs, some employ positioning pins for blade fixation. However, these pins are prone to deformation, which can affect the reliability of the clamping mechanism (such as in wedge-type tools). On the other hand, some designs offer more reliable positioning but have complex structures and poor manufacturing processes (like lever or plug types).
The key-guided tension-adjustable indexable turning tool combines the advantages of reliable clamping, easy blade indexing and replacement, and a simple manufacturing process. Its structure is illustrated in Figure 1.
1. Knife pad 2. Blade 3. Key pin 4. Blade body 5. Spring washer 6. Nut Figure 1 Key-guided tension-type turning tool
This clamping system has several notable features: First, it utilizes a threaded bevel lever to apply a strong and reliable clamping force. Second, the key pin ensures smooth engagement between the knife pad and the blade body during cutting, reducing vibration and improving rigidity and stability. Third, the blade can be quickly indexed and replaced by simply adjusting the tail nut. Finally, the overall design is compact and efficient.
When designing SNU U160602FR inserts with key-guided tension-type indexable turning tools, the main cutting edge angle (kr) can typically range from 45° to 90°, with 75° being the most common. The rake angle (gog) is usually between -8° and -15°, while the clearance angle (lsg) ranges from 0° to 10°, often set at 0°. The nose radius (erg) is generally between 80° and 90°, with 90° being standard. The side cutting edge angle (krg) should be between 45° and 90°.
The keyway on the sipe must meet H9/h9 precision, while the key slot in the blade body requires D10/h9 (or F7/h6). The key pin’s cylindrical surface and blade hole must be machined to C11/h11 (or B12/h12), and the dynamic fit between the cylinder and the cutter body must be B12/h12. By adjusting the tail nut, the blade can be securely clamped or released, enabling rapid indexing and replacement.
To ensure secure clamping and prevent loosening due to vibration, a spring washer is placed between the nut and the cutter body. This helps maintain close contact between the blade and the two right-angled base surfaces of the sipe.
In terms of manufacturing, the cutter body is typically made of 45 steel, which is forged to enhance internal toughness. The heat treatment hardness should be maintained between 38–42 HRC. If too hard, the body may crack under load; if too soft, it may deform or create depressions under chip pressure, weakening support and possibly causing blade breakage.
The sipes on the cutter body are milled, and the keyway must be perpendicular to the two right angles. To ensure this, the bottom of the sipe and the two right-angled bases are processed simultaneously using a machine that guarantees verticality and parallelism. Key pins, which bear the cutting load, are made of 40Cr or 45 steel (tempered or hardened to 35–38 HRC). Their size precision is high, with surface roughness between Ra 1.6–3.2 μm. The contact area between the key pin’s cylindrical surface and the blade hole should cover at least 1/2 to 2/3 of the blade thickness. To achieve this, the root of the key pin is ground 0.2–0.4 mm on a tool grinder.
The knife pads are made of 40Cr or 45 steel (normalized). Their parallelism must be within 0.01–0.03 mm, and the surface roughness should be Ra 6.3–3.2 μm.
For application, when roughing, the maximum depth of cut (ap) is determined first, followed by a larger feed rate (f) based on blade strength and machine capacity. Cutting speed (v) is then adjusted according to machine power. For deep cuts, narrow chipbreaker grooves may lead to chipping, so the cutting parameters should be adjusted accordingly.
During finishing, a large rake angle insert with a chipbreaker groove is recommended to reduce cutting forces and improve surface quality. High cutting speeds are preferred, with reduced ap and f, but the cutting layer thickness should not be less than 0.05 mm to avoid surface hardening.
Table 1 provides reference cutting speeds for different materials, taking into account varying ap and f values. When working with low-carbon steels, stainless steels, or other ductile materials, single-sided, positive quadrant inserts with good chip control are recommended.
Finally, when inserting the blade, ensure the underside is in full contact with the knife pad, and the sides are aligned with the two right-angled bases of the sipe to prevent vibration. Blades should be indexed or replaced when wear reaches VB = 0.3 mm. This tool is also suitable for machining hardened steels, gray cast iron, and can be adapted for triangular thread turning, boring, and milling operations.
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