Kunshan Meiyaxing Hardware Machinery Co., Ltd., a direct branch of Hong Kong Meiya International Trading Co., Ltd., owns its own cutting tool brand: MANF, and engages in the sales and operation services of CNC cutting tools. It provides tungsten carbide milling cutters, milling inserts, turning inserts, grooving and parting inserts, drilling and boring inserts, multi-functional inserts, threading inserts, and other indexable inserts and their matching tool holders and tool holders. Furthermore, it has established long-term strategic partnerships with several well-known manufacturers, jointly developing R&D, design, and production teams, utilizing advanced equipment and continuously innovating technological capabilities. Committed to mutual cooperation and a technology-service-oriented approach, it forms a mutually supportive industrial chain to solve various processing problems for manufacturing enterprises.
In machining... In machining, the choice of milling inserts directly affects machining efficiency, workpiece quality, and tooling costs. Many operators have experienced this frustration: the same milling cutter produces smooth and successful machining on machine tool A, but frequently chips and breaks on machine tool B. The key issue often lies not in the "quality" of the tool itself, but in whether the matching logic between the insert and the specific machining scenario is truly understood. This article systematically outlines the key points for selecting general-purpose milling inserts from four dimensions: insert material, coating technology, geometric parameters, and matching with the machining scenario.
III. Geometric Parameters-The Efficiency Code Hidden in Angles
The geometric parameters of the insert are key variables affecting cutting smoothness, tool strength, and machining quality. Understanding and rationally selecting these angles is a crucial step in choosing the right insert.
3.1 Rake Angle (γ₀) – Sharpness or Strength?
The size of the rake angle primarily resolves the conflict between tool tip strength and sharpness. When machining soft materials, a large rake angle (12°~25°) is preferable to reduce cutting forces and improve surface quality. When machining hard, brittle, or high-hardness materials, a smaller rake angle, or even a negative rake angle (0°~-10°), should be used to enhance the tool tip's impact resistance and prevent chipping. Generally, the rake angle is selected between -5° and 25°, with a smaller value for roughing and a larger value for finishing.
3.2 Clearance Angle (α₀) – The "Protective Charm" of the Back Face
The clearance angle reduces friction between the back face and the workpiece surface, and is generally selected between 6° and 12°. A larger clearance angle (10°~15°) can be used for finishing to reduce friction and achieve better surface quality; a smaller value is used for roughing to ensure tool tip strength. When machining materials with high hardness, a smaller clearance angle should also be used to enhance tool tip strength.
3.3 **Principal Cutting Edge Angle (κᵣ)** – The "Conductor" of Cutting Force Direction
The principal cutting edge angle is generally selected between 30° and 90°, directly determining the magnitude of the radial cutting force and the heat dissipation area.
* **90° Principal Cutting Edge Angle:** Suitable for square shoulder milling, stepped surface milling, and slot milling. It has good versatility and is widely used in single-piece and small-batch machining. However, it has a large radial cutting force, is prone to vibration, and requires high machine tool power and rigidity.
* **45° Principal Cutting Edge Angle:** The radial cutting force is significantly reduced, approximately equal to the axial cutting force. The cutting load is distributed along a longer cutting edge, resulting in good vibration resistance and a low insert breakage rate. It is suitable for machining applications where the spindle overhang of a boring and milling machine is long.
* **75° Principal Cutting Edge Angle:** Between the two, it balances radial force control and depth of cut capability, suitable for roughing.
3.4 **Tool Tip Radius (rε)** – A Balance Between Strength and Precision
The larger the tool tip radius, the higher the tool tip strength and the longer the tool life (for every 0.2 increase in radius...) While a larger tool tip radius (rε = 0.8~1.2 mm) increases cutting edge strength and can withstand greater cutting loads, a smaller tool tip radius is preferred for roughing operations. Generally, rε ≤ 0.8 × minimum depth of cut; otherwise, "tool deflection" errors are likely to occur.
IV. Selection Based on Workpiece Material – Understanding ISO Grouping ISO standards classify workpiece materials into six main groups (P, M, K, N, S, H) based on their machinability. Each group has unique characteristics in terms of machinability. The ISO grouping markings on the inserts are the most direct reference for selection.
· P Group – Steel: The largest material group in metal cutting, encompassing everything from non-alloy steel to cast steel. Steel generally has good machinability, but this varies significantly depending on carbon content and hardness. Carbide inserts are the first choice for machining steel. For roughing, YT-type inserts (such as YT15) are suitable, while cermet inserts are suitable for finishing.
M Group – Stainless Steel: Cutting stainless steel generates a large amount of heat and is prone to groove wear and built-up edge. Carbide inserts with a high cobalt content (ISO M-type inserts) should be used, paired with a sharp cutting edge and a large rake angle (γ₀=10°~15°) to reduce cutting forces and suppress built-up edge. Tests show that M-type inserts have a life more than 35% longer than general-purpose P-type inserts.
K Group – Cast Iron: Cast iron is a short-chip material containing silicon carbide (SiC), which severely wears the cutting edge. For machining cast iron, high-wear-resistant carbide inserts (such as YG-type) should be used. CBN or ceramic inserts can be used for high-speed finishing.
Group N – Non-ferrous metals: Includes relatively soft metals such as aluminum, copper, and brass. Aluminum alloys with a silicon content of 13% or higher are highly abrasive and should be machined with PCD inserts. Inserts with sharp cutting edges typically achieve higher cutting speeds and longer tool life.
Group S – Heat-resistant alloys (high-temperature alloys/titanium alloys): These materials are sticky, prone to built-up edge, work hardening, and heat generation, making them more difficult to machine than stainless steel and resulting in shorter cutting edge life. Ceramic inserts or high-performance carbide tools are recommended for machining Group S materials.
Group H – Hardened steel: Includes steel with a hardness of 45-65 HRC and chilled cast iron. These materials are difficult to machine, generating significant heat during cutting and severely wearing down the cutting edge. CBN tools or superhard carbide tools are preferred for machining Group H materials.
V. Selection by Machining Task – Face Milling, Square Shoulder Milling, and Slot Milling
Depending on the machining task, the appropriate type of milling insert should be selected. The three most common milling types are face milling, square shoulder milling, and slot milling, each with different requirements for insert geometry and cutting edge performance.
· Face Milling: When machining flat surfaces, use face milling cutters. The recommended cutter diameter is 1.2 to 1.5 times the workpiece width. A 45° lead angle face milling cutter is a cost-effective choice; the insert can be indexed multiple times, and it is suitable for materials such as steel, cast iron, and stainless steel. The 45° lead angle cutter offers better depth of cut than a 90° cutter and also provides better vibration resistance.
Square Milling: When machining flat surfaces or steps with square shoulders, use a 90° lead angle square shoulder cutter. This type of cutter is versatile and particularly suitable for single-piece, small-batch machining. For shallow depth-of-cut applications, consider using inserts with a straight cutting edge design to achieve a more stable cutting thickness.
Slot Milling: When machining slots and cavities, select an end mill or slot milling insert with an appropriate diameter based on the slot width and machining depth. The ratio of slot width to cutter diameter should be controlled between 1.0 and 1.2. When the slot depth exceeds three times the cutter diameter, a layered milling strategy is required. Circular insert milling cutters offer high metal removal rates and good impact resistance in roughing and profile milling.
Difference between roughing and finishing: Roughing aims for high material removal rate, requiring inserts with a principal cutting edge angle of 75°~90° and a large tip radius (0.8~1.2 mm). Finishing demands high surface quality, requiring inserts with small feed rate, shallow depth of cut, sharp cutting edge, and finishing edge. A surface roughness of Ra below 0.8 μm can be achieved with a relatively small feed rate.
VI. Selection Process and Common Misconceptions
6.1 Systematic Four-Step Selection Method
Step 1: Identify the workpiece material-Confirm which group (P/M/K/N/S/H) the material belongs to; this is the most important determining factor.
Step 2: Determine the machining type-Face milling, shoulder milling, or slot milling? Roughing or finishing?
Step 3: Match insert parameters-Select a base material with a balance of hardness/toughness, a suitable coating, and optimized geometry.
Step 4: Verify cutting parameters-Adjust cutting speed, feed rate, depth of cut, and other parameters to a reasonable range based on machine tool power, clamping rigidity, and other factors.
· Blindly pursuing high hardness: High hardness results in poor impact resistance; for interrupted cutting, insert materials with good toughness should be prioritized.
* Ignoring coating matching: Different coatings have different properties. General-purpose coatings (such as TiN) can be used for machining ordinary steel, but heat-resistant coatings (such as TiAlN or AlCrN) must be used for machining high-temperature alloys.
* Using a single tool for everything: Roughing and finishing require completely different geometric parameters; mixing them will lead to efficiency losses or quality problems.
* Ignoring the tip radius: Choosing an excessively small tip radius for roughing will cause edge chipping; choosing an excessively large radius for finishing will increase cutting forces and vibration, affecting surface quality.
In short, selecting a general-purpose end mill insert is a systematic project that requires comprehensive consideration of the matching relationship between four major factors: workpiece material, machining method, insert material and coating, and geometric parameters. Only by organically integrating these four factors can a balance between high efficiency and low cost be achieved while ensuring machining quality.
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Contact us:Company name:Kunshan Meiyaxing Hardware Machinery Co., Ltd;Tel:8618962438699;Address: Room 3003, Building 3, Zhengtailong, No. 1288 Chengbei Middle Road, Kunshan City, Jiangsu Province, China;Email:myxcuttingtools@gmail.com;Website: https://www.myxcuttingtools.com
