Complete Guide To Chipper Knife Steel: Choose The Right Blade Material

Complete Guide to Chipper Knife Steel

Chipper knife steel is a series of professional high-alloy tool steel designed to withstand heavy impact, continuous vibration and severe abrasive wear during wood chipping. Chipper blades cut dense logs, hard knots, mud-filled branches, and occasionally hit stones, nails and other hard foreign impurities. Thus, qualified blade steel must reach a balanced metallurgical performance: anti-crack fracture toughness and long-term cutting-edge wear resistance.

This guide sorts out mainstream steel grades for industrial chippers, sawmill fixed chippers and domestic garden wood shredders, classified by practical working performance.

1. Modified A8 (A8 Mod) — Top Standard Chipper Blades Steel

Industry Status: Named exclusive “Chipper Knife Steel” by Carpenter Technology and global premium steel mills. It is the factory standard material for European & American heavy-duty drum & disc wood chippers.

Core Features: Air-hardening 8% chromium cold-work tool steel. Its performance balances perfectly between high-toughness S7 steel and high-wear D2 steel.

Field Performance: Better wear resistance than S7, far higher anti-chipping toughness than D2. It hardly chips or cracks when hitting knots, silt and small stones. Standard finished hardness: 56–60 HRC.

Equivalent Global Grades: Böhler K329, K353, DIN X48CrMoV8-1-1 (1.2360)

2. D2 Tool Steel — Wear-First Grade

Application: Fixed sawmill chippers for processing clean, debarked and dry timber only.

Core Features: High-carbon & high-chromium tool steel, high hardness up to 60–62 HRC, excellent edge retention ability.

Field Performance: Resists bark and wood fiber abrasion effectively, extending blade service life between sharpening. Due to limited toughness caused by internal coarse carbides, it can crack or chip heavily once hitting stones or metal nails.

Equivalent Global Grades: DIN 1.2379, Cr12MoV, SKD11

3. S7 Shock-Resistant Steel — Maximum Impact Toughness

Application: Scrap wood recycling yards, heavy impurity wood processing, waste timber shredding jobs.

Core Features: Low-carbon & low-chromium anti-impact tool steel, top-level impact resistance across all chipper steel grades.

Field Performance: Blades only bend or dent under hard impact, no breakage or edge chipping. The main disadvantage is weak wear resistance, which means faster edge dulling and more frequent sharpening for high-output work. Standard finished hardness: 54–57 HRC.

4. M2 HSS High Speed Steel — High Red Hardness Grade

Application: Household branch shredders, small high-speed light-duty disc chippers.

Core Features: Tungsten-molybdenum high speed steel, stable hardness under high cutting temperature (good red hardness).

Field Performance: Ideal for cutting softwood and fresh green branches. Brittle fracture may happen under sudden heavy impact.

Equivalent Global Grade: SKH-51

5. Other Special-Purpose Blade Steel

5.1 High Carbon Steel (1075 / 75Cr1)

Low cost, basic wear resistance. Only used for light garden branch cutting, not suitable for heavy industrial chipping work.

5.2 Tungsten Carbide / Carbide Coated Blade

Ultra-high hardness, super long service life. Extremely brittle and high production cost. Used for premium heavy-duty chippers with clean raw materials and long maintenance cycles.

5.3 Saw Blade Base Steel (8670, SKS5, SKS51)

Custom thin-blade base material, good plate toughness, rarely used as main cutting blade for heavy chippers.

5.4 Special Steel for Veneer Knives

DIN 1.2345, 1.2362, 1.2631, 1.2550: Custom material for veneer machinery, not universal chipper blade steel.

5.5 Regional Traditional Steel Grades (China & CIS)

• 6CrW2Si / 6ХВ2С: Old-type wood cutting blade steel for early-model chippers

• H13 (4Cr5MoSiV1): Hot work die steel, not for normal ambient wood chipping

• 9CrSi, SK5: Low-cost light-duty carbon blade steel for small branch cutters

• 5ХНВС: Obsolete structural steel, not recommended for cutting blades

Steel Performance Comparison Chart

Quick Steel Selection Rules

Blade selection depends on three core factors: wear resistance, impact toughness and procurement cost.

1. Wood with knots, mud, construction sundries: Choose A8 (first choice); Choose A8 Mod for extreme heavy impact working conditions

2. Clean, dry, debarked industrial wood: Choose D2 / M2 for longer blade service life

3. Long-term waste wood recycling: Choose S7 or A8 Mod for best anti-break performance

Professional Heat Treatment Tip

To maximize blade service life, standard heat treatment for A8 air-hardening steel: Air Hardening → Triple Tempering → Precision Edge Grinding. This process eliminates internal quenching stress and avoids blade cracking during operation.

Note: D2 and S7 cannot share the same heat treatment parameters as A8, which will cause uneven hardness and hidden cracking risk.