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What is a high-speed steel forming knife
High Speed Steel Forming Tool (HSS) is a cutting tool designed specifically for "one-time processing of complex shaped workpieces" using high-speed steel (HSS) as the core material. It is widely used in machining scenarios such as turning, milling, and planing in mechanical manufacturing. Its core features are "balancing material toughness and cutting performance" and "customizable matching of workpiece shape", which can replace multiple ordinary cutting processes and directly process workpieces with specific contours (such as steps, arcs, grooves, threads, etc.), greatly improving processing efficiency and accuracy.Sources：www.0755oml.com | PublishDate：2025.09.23
1、 Core definition: Why is it called a "high-speed steel forming knife"?
From the name, its key attributes can be broken down to understand its essential differences from ordinary cutting tools:
Material: High speed steel (HSS) - the core high-speed steel that determines cutting performance (such as W18Cr4V, W6Mo5Cr4V2 and other grades) is a high alloy tool steel containing tungsten, chromium, vanadium and other alloy elements. Its core advantage is high high-temperature hardness (at cutting temperatures of 600-650 ℃, the hardness can still maintain HRC60 or above, far exceeding the 200-300 ℃ tolerance limit of ordinary carbon tool steel), good toughness (not easy to break edges, suitable for intermittent cutting or processing of materials with high hardness), which allows it to meet the cutting needs of medium and high-strength metals (such as 45 # steel, stainless steel, cast iron), and its service life is 3-5 times longer than ordinary cutting tools.
Function: Forming cutting - the key factor determining machining efficiency. The cutting edge of ordinary cutting tools (such as ordinary turning tools and milling cutters) is often a "single shape" (such as a plane or a straight line), which requires multiple adjustments to the tool angle and path in order to machine complex workpieces (such as machining a "shaft type part with circular arc steps", ordinary cutting tools need to first turn the outer circle, then turn the steps, and mill the circular arc, with at least 3 processes); The cutting edge shape of the high-speed steel forming knife is perfectly matched with the contour of the workpiece (customized according to the workpiece drawing in advance), and multiple cutting processes can be completed in one clamping (the above-mentioned shaft parts can be processed with a forming knife, and one process can be formed), so it is also called "composite forming knife" or "special forming knife".
2、 3 core features: key advantages in adapting to complex machining scenarios
High speed steel forming knives can be widely used in mechanical processing due to their unique advantages in efficiency, precision, and applicability, as follows:
High processing efficiency: The core logic of "one-time molding" replacing "multiple cutting" is to "reduce the number of processes and clamping" - every additional clamping of the workpiece not only increases operation time, but may also reduce accuracy due to "clamping errors" (such as workpiece positioning deviation). The high-speed steel forming knife compresses the originally required 2-5 processes into one through "customized cutting edges", increasing processing efficiency by 2-5 times. Example: To process "bolts with trapezoidal threads", ordinary cutting tools need to first turn the outer circle and then turn the threads (at least 2 processes); The high-speed steel ladder shaped thread forming tool can complete the cutting of "outer circle+thread" in one go, reducing the single piece processing time from 10 minutes to 3 minutes.
Stable machining accuracy: Avoiding "multiple clamping errors". In mechanical machining, "multiple clamping" is the main source of accuracy deviation (for example, after the first clamping of the outer circle of the lathe, the second clamping may cause slight deviation of the workpiece, resulting in subsequent machining steps not being concentric with the outer circle). The high-speed steel forming knife directly ensures the relative accuracy of various parts of the workpiece (such as step height difference, arc radius tolerance) through "one clamping, one cutting", and the accuracy can be stably controlled at IT8-IT10 levels (ordinary multiple cutting accuracy is mostly IT11-IT13 levels), especially suitable for mass production with high requirements for "contour consistency" (such as automotive parts, agricultural machinery parts).
Good material toughness: Suitable for various difficult to machine scenarios. Compared to hard alloy forming knives with higher brittleness (although harder, they are prone to breakage under impact), high-speed steel forming knives have significant toughness advantages and can cope with two types of complex processing scenarios:
Intermittent cutting: When machining workpieces with grooves or gaps on the surface (such as shafts with keyways), the cutting edge will repeatedly "cut in and out" to withstand impact loads. The toughness of high-speed steel can prevent edge breakage;
Processing low to medium hardness materials: For materials such as 45 # steel (hardness HB200-250) and gray cast iron (HB180-220), high-speed steel has slower cutting edge wear and does not require high-frequency tool replacement (hard alloy tools are prone to "sticking" when processing soft materials, and their lifespan is shortened).
3、 Applicable scenarios and limitations: Clarify what it can and cannot do
1. Core applicable scenarios
Batch processing of complex contour workpieces, such as automotive gearbox gear shafts (with multiple steps and arcs), agricultural plows (with specific blade curves), household appliance accessories (metal shells with grooves), etc., requires ensuring "multi piece consistency" and pursuing efficiency;
Low to medium hardness metal processing: Processing materials with hardness ≤ HB300 (such as 45 # steel, 20 # steel, gray cast iron, aluminum alloy), high-speed steel has a good balance between toughness and cutting performance;
Intermittent cutting or light cutting: such as machining shaft parts with holes or grooves, or forming small diameter (≤ 50mm) workpieces.
2. Main limitations
Not applicable to high hardness materials: When processing materials with a hardness greater than HRC30 (such as quenched steel and high-speed steel itself), the cutting temperature of high-speed steel will exceed the tolerance limit, and the tool wear will be extremely fast (requiring replacement of hard alloy or ceramic forming tools);
The processing efficiency is lower than that of hard alloy knives: When continuously cutting high hardness materials (such as stainless steel 304), the cutting speed of hard alloy forming knives (up to 100-150m/min) is much higher than that of high-speed steel forming knives (only 30-60m/min), and the efficiency difference is significant during mass production;
High customization cost: Each molding tool needs to be designed and ground separately according to the contour of the workpiece, and the cost of customizing a single tool is 5-10 times higher than that of ordinary tools. It is not suitable for small batches (<100 pieces) or multi variety trial production scenarios.
