Double shaft shredder blades Product Manual: Material Selection, Operation, Maintenance & Full Cost Analysis
ALAS is an experienced manufacturer of double shaft shredder blades. We supply reliable, long-lasting blades for waste recycling and solid waste processing industries worldwide. This manual introduces our products, material options, field operation rules, daily maintenance and full life cycle cost calculation. It helps buyers and plant operators pick suitable blades, control running costs and extend product service life.
Introduction
Double shaft shredder blades are key wearing parts for shredding machines. They keep direct contact with raw materials during operation. Statistics show that blade replacement, repair and resharpening costs account for 60% to 70% of total equipment maintenance expenses.
ALAS blades are made of premium raw materials, processed with standard heat treatment and precision machining. Our products deliver two to three times longer service life than regular blades. Proper selection, correct operation and routine maintenance can reduce overall operating costs by more than 40%.
This manual uses question-and-answer content, data tables and step-by-step guides to fit actual production and international purchasing work.
Part 1 Basic Knowledge & Product Features
1. ALAS Double Shaft Shredder Blades vs Single Shaft Shredder Blades
ALAS double shaft shredder blades are claw style cutters. They are installed in pairs on two parallel low-speed rotating shafts. The blades break materials through shearing, tearing and stretching. Different from single shaft blades, our products work without screen mesh. They handle bulky waste and materials mixed with metal parts well. Matched with machines featuring overload reversal function, ALAS blades perform excellently against material jams.
| Comparison Items | ALAS Double Shaft Shredder Blades | Single Shaft Shredder Blades |
| Installation | Two parallel shafts, blades arranged in staggered way | Single main shaft plus fixed counter blade |
| Speed & Torque | 5.5-10 rpm, high torque | 50-150 rpm, medium torque |
| Crushing Method | Shearing, tearing and stretching | Cutting and extrusion, rely on screen mesh for discharge |
| Applicable Materials | Scrap car bodies, tires, mixed waste, metal drums and other large materials | Plastic, wood, film and materials with uniform texture |
| Jam Solution | Machine reverses automatically to remove foreign objects | Stop machine for manual cleaning; screen mesh easy to damage |
| Discharge Size Control | Determined by blade thickness and claw quantity | Determined by screen mesh hole size |
| Normal Service Life | 300-600 hours (varies by material) | 200-400 hours |
2. Working Process of ALAS Double Shaft Shredder Blades
Two shafts rotate in opposite directions at low speed. Blade claws grab materials and form shear areas at staggered positions. Materials are torn and cut repeatedly until the size is smaller than blade gaps, then fall down naturally. When hard foreign objects appear, the machine reverses automatically to protect blades from damage.
Grab Materials
Hook-shaped cutting edges catch large and fluffy materials. Anti-slip structure prevents materials from spinning together with shafts.
Tear Materials
Blades on two shafts squeeze each other to generate strong tearing force and split materials.
Reduce Particle Size
Continuous cutting makes materials smaller. Blade thickness decides the width of final materials.
Automatic Discharge
Qualified small materials drop from the machine bottom. No screen mesh is needed, so blockage rarely happens.
Overload Protection
Hydraulic or torque sensors trigger shaft reversal for 2 to 3 seconds under overload. Hard impurities are removed and the machine returns to normal work.
3. Industries That Need High Performance ALAS Double Shaft Shredder Blades
Metal recycling, electronic waste processing, waste tire recycling, municipal waste pre-treatment, large waste disposal and construction waste processing all require high performance blades. Materials in these industries are hard and complex, mixed with sand, stone and metal scraps. Ordinary blades wear out within 200 working hours. ALAS heavy-duty blades are the practical choice for stable long-term production.
| Industry | Common Materials | ALAS Recommended Materials | Hardness (HRC) | Main Performance Requirements |
| Metal Recycling | Scrap car bodies, steel scraps, aluminum profiles | H13, Carburized SKD-11 | 50-55 / 58-62 | Impact resistance, high temperature resistance |
| E-waste Processing | Circuit boards, equipment chassis, waste home appliance shells | Cr12MoV, Tungsten Carbide Tipped | 58-62 | Wear resistance, anti-chipping |
| Waste Tire Recycling | All-steel radial tires | M2 High-speed Steel, Alloy Tipped | 63-66 | High strength, anti-fatigue fracture |
| Plastic Recycling | Plastic drums, bottles, plastic film | 9CrSi, SKD-11 | 56-62 | Sharp edge, anti-winding |
| Municipal Solid Waste | Mixed waste, textile, kitchen waste | Hadfield Steel, 42CrMo | Work-hardened | High toughness, impact resistance |
| Construction Waste | Mixed waste with sand, steel bars and wood | Hadfield Steel, H13 | Over 45 after impact | Abrasion resistance, impact resistance |
Part 2 Material Types & Technical Parameters
4. Material Selection Guide
ALAS provides five common steel grades for different working conditions: H13, SKD-11, Hadfield Steel, 9CrSi and M2 High-speed Steel. Select materials according to material hardness and impact frequency on site.
H13 works well under high temperature and heavy impact, suitable for light metal and heat-generating materials. SKD-11 and Cr12MoV offer great wear resistance for hard plastic and metal scraps. Hadfield Steel becomes harder under impact, ideal for waste mixed with sand and stone. 9CrSi is low cost but brittle, only fit for soft materials. M2 high-speed steel combines good wear resistance and heat resistance for hard metal processing.
| Material | Steel Type | Hardness (HRC) | Heat Resistance | Impact Toughness | Wear Resistance | Sharpening Times | Cost Level | Normal Service Life (Hours) |
| H13 (SKD61) | Hot Work Tool Steel | 50-55 | Excellent | Good | Medium | 3-4 | Medium-High | 300-450 |
| SKD-11 (Cr12MoV) | Cold Work Tool Steel | 58-62 | Fair | Medium | Excellent | 4-5 | High | 400-600 |
| Hadfield Steel (Mn13) | Austenitic Steel | Initial 180-220 HB, over 45 HRC after impact | Poor | Excellent | Medium, good anti-abrasion | Hard to resharpen | Medium | 250-350 |
| 9CrSi | Alloy Tool Steel | 56-60 | Poor | Poor | Medium | 2-3 | Low | 150-250 |
| M2 High-speed Steel | High-speed Tool Steel | 63-66 | Good | Fair | Good | 3 | Very High | 350-500 |
Note: The service life data is tested with continuous operation on medium hard mixed waste. Actual service life changes with raw materials, blade gaps and working environment. All ALAS blades adopt standard heat treatment to keep stable performance.
Practical Selection Advice
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For construction waste containing 10% to 20% sand and stoneChoose ALAS Hadfield Steel blades. Sand and stone cause serious abrasion. Hadfield Steel gains higher surface hardness under impact while keeping strong internal toughness to avoid breakage. SKD-11 has high hardness but low toughness, easy to chip when hitting gravel.
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For 24-hour continuous processing of aluminum profiles with a small amount of iron parts, blades need resharpening every two weeksChoose ALAS H13 blades. Aluminum processing creates large friction heat. H13 performs much better than SKD-11 at high temperature and resists impact from iron scraps. SKD-11 has good wear resistance at room temperature but wears fast under long-time heating.
Part 3 Structure and Specification Selection
6. Claw Quantity and Discharge Size
Claw quantity is an important specification of ALAS double shaft shredder blades. More claws mean more cutting times per rotation and finer discharge size.
| Claw Quantity | Usage Type | Discharge Size | Material Grabbing Ability | Cutting Times per Rotation | Application Scenarios |
| 2-3 | Coarse shredding | 80-200 mm | Strong | Low | Bundled steel, large timber, whole vehicle bodies |
| 6 | General use | 40-100 mm | Good | Medium | Industrial waste, plastic drums, common e-waste |
| 8 | Fine shredding | 20-60 mm | Medium | High | Waste tires, aluminum profiles, circuit boards |
| 12 | Ultra-fine shredding | 10-30 mm | Weak | Very High | Plastic pelletizing, rubber grinding, small electronic parts |
Supplement: ALAS also supplies customized mixed claw blades for high-end machines, to balance grabbing ability and shredding fineness.
7. Blade Thickness Selection
Blade thickness decides discharge width and impact resistance. ALAS provides full range of thickness options for different working conditions.
| Blade Thickness | Standard Discharge Width | Impact Resistance | Application Scenarios |
| 10-20 mm | 10-20 mm | Weak, easy to deform | Plastic film, woven bag, paper, chemical fiber |
| 20-30 mm | 20-30 mm | Medium weak | Hard plastic bottles, small e-waste, rubber strips |
| 40-50 mm | 40-50 mm | Medium strong | Wood pallets, mixed municipal waste (mainstream size) |
| 60-75 mm | 60-75 mm | Strong | Scrap car bodies, engine shells, heavy steel |
8. ALAS Modular Quick Change Blades
ALAS modular blades consist of three parts: base hub, replaceable cutter claws and auxiliary guard teeth. Users only need to change worn claws instead of taking down the whole shaft. Traditional blade replacement takes 4 to 6 hours. ALAS modular design cuts downtime to 30 to 60 minutes.
Base hub: Made of 42CrMo, fixed on main shaft, long service life.
Replaceable cutter claw: Core cutting part, available in H13 and SKD-11, easy for single replacement.
Auxiliary guard tooth: Protect base hub, can be installed reversely for second use.
Blade Replacement Steps
Cut off power, lock hydraulic system and hang warning signs on site.
Open the shredding chamber cover with hydraulic system.
Turn the shaft manually to move the target claw to the access opening.
Loosen fixing bolts with torque wrench. Replace deformed bolts together.
Tap stuck blades gently with copper rod. Do not use steel hammer.
Clean dirt and oil on mounting surface with steel brush and compressed air.
Install new claws, apply anti-seize compound on contact surface. Tighten bolts at standard torque 200-280 N·m.
Measure blade gap with feeler gauge. Standard gap: 0.3-0.8 mm.
Run machine with no load for 2 minutes to check abnormal noise. Then run with materials at low speed for 5 minutes.
Record replacement position, time and operator information.
Part 4 Daily Maintenance, Sharpening and Troubleshooting
9. Blade Sharpening Rules and Standards
Check blade edges thoroughly every 200 to 300 working hours. Resharpen blades at once when edge wear exceeds 0.5 mm or partial chipping appears.
| Inspection & Sharpening Items | Execution Standards |
| Sharpening Cycle | Every 200-300 working hours, or after processing 200-400 tons of materials |
| Primary Edge Angle | 30°±2°, keep same as original design |
| Secondary Edge Angle | 45°±2° |
| Maximum Single Grinding Depth | 1.5 mm (from edge to blade back) |
| Post-sharpening Treatment | Polish edge to 0.05-0.1 mm radius to remove burrs |
| Maximum Temperature During Grinding | Below 200℃. Use water cooling or CBN grinding wheel |
| Maximum Sharpening Times | SKD-11 & H13: 4-5 times; High-speed Steel: 3 times; 9CrSi: 2-3 times |
| Scrap Standard | Thickness loss over 15% of original size, penetrating cracks, chipping depth over 5 mm |
Important note: Dry grinding will make edge temperature over 250℃ and cause blade softening. Hardness will drop below 40 HRC and service life reduce by over 70%. Water cooling is required during all grinding work.
10. Common Faults and Solutions
Fault 1: Frequent small chipping on blade edges
Hard metal parts mixed in materials: Install magnetic separator and metal detector on feeding line to remove impurities automatically.
Blade gap less than 0.2 mm, blades hit each other: Stop machine and adjust gap to 0.3-0.8 mm with gaskets.
Wrong material selection: Brittle 9CrSi blades used for hard materials. Replace with ALAS H13 or high-speed steel blades.
Loose fixing bolts cause blade vibration and collision: Check bolt torque before daily startup. Use lock washers and thread locking adhesive.
Fault 2: Blade breakage and penetrating cracks
Raw material forging defects and material segregation: Return defective products and ask for metallographic inspection report.
Unqualified heat treatment and insufficient tempering: Purchase qualified finished blades from ALAS.
Long time overload operation: Reduce feeding size and add pre-shredding equipment. Upgrade to higher strength blades.
Fault 3: Blade gap over 1.0 mm, low production efficiency
Worn shaft bearings lead to larger shaft distance: Check bearing clearance and replace worn bearings.
Worn blade base or missing sealing gaskets: Dismantle blades for measurement. Add gaskets or install new ALAS blades.
Blade Gap Adjustment Steps
Cut off power and clean dirt on blade surface.
Select 3 to 5 points along shaft direction, measure minimum gap between paired blades with feeler gauge.
Loosen bearing housing bolts.
Adjust eccentric sleeves or add / remove gaskets under bearing housings to fine tune shaft position.
Retighten bolts and recheck gap. Gap tolerance along the whole shaft: ±0.05 mm.
Run machine with no load for 2 minutes. Start formal production if no friction or abnormal noise.
11. Blade Welding Repair Rules
On-site hardfacing repair is allowed for carbon steel and low alloy steel blades (42CrMo base, 9CrSi) without penetrating cracks and carbide tips. Recommended welding rods: D266 and D397.
On-site welding is not allowed for ALAS H13, SKD-11, high-speed steel and carbide-tipped blades. Send damaged blades back to ALAS factory for professional laser cladding repair.
Welding Steps
Grind damaged area to remove oxide and dirt, expose clean metal surface.
Preheat the whole blade to 150℃~250℃ to prevent cold cracks after welding.
Conduct multi-layer hardfacing with specified welding rods. Remove slag after each layer.
Wrap blades with asbestos cloth for slow cooling after welding. Then do low temperature tempering at 200℃ for 2 hours.
Grind blades back to original size and shape.
Complete dynamic balance test. Allowable unbalance: less than 5 g·cm per shaft.
Cases Forbidden for On-site Welding
Carbide-tipped blades: Welding high temperature will damage internal brazing material and cause carbide to fall off.
Blade chipping depth over one third of total thickness: Structural damage cannot be fixed by welding.
Blades with large penetrating cracks.
Part 5 Cross-border Procurement and Full Cost Analysis
12. How to Choose Cost-effective ALAS Double Shaft Shredder Blades
Follow three steps for selection: analyze material conditions, confirm blade specifications according to discharge size, calculate full life cycle cost including product price, international freight and import tariff. Run 200-hour field test with sample blades finally.
Step 1 Analyze working conditions
Material hardness: Select ALAS SKD-11 or high-speed steel for hard materials.
Impurity ratio: Choose Hadfield Steel or H13 if sand, stone and metal blocks take more than 10% of raw materials. Focus on toughness.
Continuous operation: Select re-sharpenable H13 or SKD-11 blades for 24-hour non-stop production.
Step 2 Confirm blade specifications by discharge requirement
Fine shredding (output below 30 mm): 12-claw blades, thickness 20-30 mm.
Standard shredding (output 30-80 mm): 6-8-claw blades, standard thickness 40 mm.
Coarse shredding (output over 80 mm): 2-3-claw blades, thickness over 50 mm.
Step 3 Full Life Cycle Cost Calculation (including international freight and tariff)
Calculation Formula
Total Landed Cost per Set = Ex-factory Price + Allocated International Freight + Import Tariff & Customs Clearance FeeTotal Life Cycle Cost = Annual Total Landed Cost + Annual Resharpening Fee + Annual Downtime Loss
Note: The tariff rate for metal cutting tools ranges from 5% to 15% in most countries. Unit freight reduces when order quantity increases.
Practical Calculation Case
Working condition: Annual processing volume 5,000 tons mixed waste. International freight per set: $22.14. Tariff and clearance fee: 10% of ex-factory price. Each replacement takes 8 hours downtime, labor cost: $73.68 per hour.
| Cost Items | 9CrSi Ordinary Blades | ALAS SKD-11 High Performance Blades |
| Ex-factory Price per Set | $294.74 | $736.84 |
| International Freight per Set | $22.14 | $22.14 |
| Tariff & Clearance Fee per Set | $29.47 | $73.68 |
| Total Landed Cost per Set | $346.35 | $832.66 |
| Total Processing Capacity per Set | 200 tons | 600 tons |
| Annual Consumption Quantity | 25 sets | Approx. 8.3 sets |
| Annual Total Landed Cost | $8,658.75 | $6,911.08 |
| Annual Total Resharpening Fee | $442.11 | $589.47 |
| Downtime Loss per Replacement | $589.47 | $589.47 |
| Annual Total Downtime Loss | $14,736.84 | $4,892.63 |
| Total Annual Life Cycle Cost | $23,837.70 | $12,393.18 |
Conclusion: After adding international freight and import tariff, ALAS SKD-11 double shaft shredder blades still have much lower total annual cost than ordinary blades. Longer service life and fewer replacements bring better long-term economic benefits.
Step 4 Sample Test and Bulk Order
ALAS provides material spectrum test report and heat treatment record for each batch of goods. We also supply complete customs documents for cross-border orders.
Support sample order of 1 to 2 sets for 200-hour field test. Choose international express for small samples to control logistics cost.
Check blade wear condition after test. Uniform arc wear means normal use. Adjust blade gap or change material if chipping and unilateral wear occur.
Conclusion
ALAS double shaft shredder blades are core parts that decide production capacity, energy consumption and overall maintenance cost of the whole shredding line. For international purchasing, do not judge product value only by ex-factory price. Take international freight and import tariff into full consideration.
As a professional manufacturer, ALAS supplies standard and customized shredder blades with strict quality control and stable performance. With the selection guides and maintenance rules in this manual, you can pick the most suitable blades for your working conditions and extend service life effectively.
Contact ALAS for product customization, equipment matching and one-stop purchasing service. A 200-hour sample test will verify our product quality and help you cut long-term operating costs.
