6B 20CrMnTi Double-Needle Sewing Machine Gear Set for Heavy-Duty Torque Transmission

6B 20CrMnTi Double-Needle Sewing Machine Gear Set for Heavy-Duty Torque Transmission

6B double needle machine gears are precision synchronous core transmission parts for 6B series industrial double needle sewing machines (842/845/872/875), including main shaft helical gears, upper/lower shaft spur gears, double needle synchronous bevel gears, feed gears, hook gears and duplex gears. They fit double needle synchronization, medium-thick materials, double-row stitches and tubular/flat sewing. Made of 40Cr/20CrMnTi high-quality alloy steel with quenching & tempering + induction/carburizing hardening, they feature precise double needle synchronization, high torque & wear resistance, low noise & high speed, impact resistance and stable stitches. They transmit power for double needle synchronization, upper/lower shaft drive, hook looping, feeding and thread take-up, ensuring double needle phase difference ≤±0.1mm, uniform stitch length, parallel double lines and no thread breakage on thick materials. They are key vulnerable parts for double-row sewing of medium-thick materials in apparel, luggage, shoes, hats and sofas.

Product Features

• Zero-error double needle synchronization: Special matched bevel + helical gear sets ensure phase difference ≤±0.1mm, with parallel double lines, no misalignment or needle collision.
• High torque & heavy-duty wear resistance: Module 1.0–2.0mm, thickened tooth root and HRC 52–58 tooth surface withstand 60–120N·m torque without chipping on 3–8mm medium-thick materials.
• High-speed & quiet transmission: ISO Grade 7 precision, polished surface and 0.06–0.12mm meshing clearance ensure noise ≤65dB for 2000–3500rpm operation.
• Precise upper/lower shaft linkage: Spur + bevel gear reversing combination ensures synchronization error ≤±0.08mm for efficient feeding/hooking/take-up coordination.
• Impact & fatigue resistance: No tooth breakage during frequent start/stop/thick material impact, enabling ≥7500 hours of maintenance-free operation.
• Wide medium-thick material adaptation: Fits canvas, denim, PU, thin leather and sofa fabrics with flat double stitches, no breakage or wrinkling.
• Strong interchangeability & easy maintenance: Fits Juki 842, Brother 845, Zoje 872, Hikari 875 and domestic 6B double needle machines for easy replacement.
• Automatic trimming compatible: Fast response and precise synchronization of trimming gears ensure residue ≤3mm for efficient automated sewing.

Technical Parameter Table

Main Applications

• Main shaft + upper/lower shaft gear sets for 6B series 842/845/872/875 double needle machines (core components).
• Special matched bevel + helical gear sets for double needle synchronization (key synchronous parts).
• High-speed gear sets for hook drive, feeding and thread take-up mechanisms.
• Gear parts for automatic thread trimming, reverse stitching and presser foot lift mechanisms.
• Double-row topstitching of medium-thick materials in apparel (denim, workwear), luggage, shoes, hats, sofas and tents.
• Double needle synchronous processing of 1–8mm denim, canvas, PU, thin leather and home textile fabrics.
• Replacement gears for old 6B double needle machines (Juki, Brother, Zoje, Hikari, etc.).

 Product Advantages

• Precise double needle synchronization: Matched gear sets strictly control phase for parallel double lines and attractive stitches.
• High torque & wear resistance: Alloy steel + carburizing/induction hardening prevent breakage/deformation on thick materials for long life.
• High speed & low noise: Precision tooth profile + polishing ensure smooth, quiet high-speed operation, improving workshop environment.
• Strong medium-thick material adaptation: Fits 1–8mm various fabrics with flat, secure double stitches for wide application.
• Efficient & stable transmission: ISO Grade 7 precision synchronizes upper/lower shafts, hooks and feed dog for uniform stitches and fewer breakages.
• Strong interchangeability: Fits major 6B double needle machine brands for easy installation and replacement, reducing maintenance costs.
• Impact & fatigue resistance: Withstands frequent start/stop and thick material impact for long-term stable operation.
• Cost-effective: Mass production with stable quality saves equipment operation and downtime costs for factories.

Production Process

• Raw material inspection: 40Cr/20CrMnTi checked for composition, hardness and defects to ensure no cracks.
• Cutting & forging: Steel cutting → hot forging to enhance tooth root rigidity (critical for synchronous bevel gears).
• Pre-heat treatment: Normalizing eliminates forging stress and improves machinability.
• CNC finish turning: Precision turning of gear blank OD, ID and end face ensures concentricity ≤0.02mm.
• Gear hobbing/milling: Specialized machines process tooth profiles (spiral teeth for synchronous bevel gears).
• Chamfering & deburring: Tooth end chamfering and polishing reduce noise and scratching.
• Quenching & tempering: Overall tempering (HRC 28–32) improves toughness and impact resistance.
• Tooth surface hardening: Induction hardening (spur/helical gears) or carburizing hardening (synchronous bevel/heavy-duty gears) to HRC 52–58.
• Precision grinding: ID, journal and tooth surface grinding ensures fitting accuracy and smooth meshing.
• Synchronous pairing: Double needle synchronous bevel + helical gears are lapped and screened in pairs with phase error ≤±3 arcminutes.
• Surface treatment: Blackening/phosphating + anti-rust oil for oil, dust and corrosion resistance.
• Full inspection & warehousing: Comprehensive check of dimensions, hardness, meshing precision, double needle synchronization and appearance before packaging.

Why Choose us?

• 7-axis CNC Grinding: We adopt high-precision 7-axis CNC grinding machines, holding tolerances as tight as ±5μm, ensuring gears run quietly, smoothly and with outstanding durability.
• Strong technical expertise: Our core R&D team includes doctoral and master’s professionals specializing in spiral bevel gear technology, providing strong technical support for complex projects.
• Rigorous testing & high precision: All gears undergo 100% inspection with Gleason metrology systems. We can achieve DIN 6 grade accuracy with strict control over tooth profile and direction errors, keeping our quality at the industry-leading level.
• High transmission efficiency: Our gear designs support a single-stage reduction ratio of up to 300:1, with actual transmission efficiency reaching over 95%, greatly improving energy utilization.
• Excellent durability & cost efficiency: Our gears deliver 40% lower lifecycle cost and a failure rate below 0.5%, ensuring stable long-term operation and reduced maintenance costs.
• Fast response & short lead time: Supported by our digitalized production process, we are able to shorten the delivery cycle to only 20 working days, helping you accelerate project development and launch.
• Professional custom design capability: We provide fully customized gear solutions for applications requiring high-reduction, high-speed, heavy-load, low-noise, and special small-tooth profiles, based on your actual working conditions.