Plastic Spur Gears with Steel Core – MC Nylon, S45C Hub

Plastic spur gears with steel cores (also called steel hub plastic spur gears or fused spur gears) are a composite gear construction that combines the advantages of plastic gear teeth with the shaft interface reliability of a steel hub. The engineering plastic gear body — typically MC602ST nylon — provides the tooth form, delivers the noise reduction, self-lubrication, corrosion resistance, and lightweight properties of a plastic gear, while the S45C or stainless steel hub insert provides a dimensionally stable bore, a reliable keyway for torque transmission, and resistance to the bore enlargement and key fretting that are the primary failure modes of all-plastic gears under repeated loading and thermal cycling.

Korea Ever-Power's plastic spur gears with steel cores are designed so that the fused parts are stronger than the teeth themselves — the joint between the steel hub and the nylon gear body will not fail before the nylon tooth fails under overload. This design assurance is the key quality criterion for the steel core fusion method: a steel-core gear that fails at the hub-nylon interface before the tooth is a fabrication failure, not a design-rated overload. Korea Ever-Power's fusion process achieves the required bond strength through controlled insert moulding parameters.

Superior to Injection-Moulded PA

MC nylon has tensile strength approximately 20–30% higher than standard injection-moulded PA6, and impact strength approximately 40% higher. The denser crystalline structure also reduces moisture absorption by approximately 15–20% compared with PA6 — improving dimensional stability in humid environments. For gear tooth surfaces that are subject to rolling/sliding contact, the superior hardness and surface quality of MC nylon compared with PA6 produces lower wear rates and longer service life.

Oil Impregnation — Extended Dry Running

The oil incorporated in MC602ST's matrix provides initial lubrication to the tooth contact zone during the break-in period and under lightly loaded dry running conditions. This reduces the tooth surface temperature at contact during starting, extends the run-without-grease capability, and produces a lower coefficient of friction against a mating steel gear than standard MC nylon. In food processing equipment where external lubrication is prohibited, MC602ST's inherent lubricity is a safety and compliance advantage.

Tooth Hardness 115–120 HRR

HRR (Rockwell R scale) is the standard hardness measure for engineering plastics — metals are typically measured on the HRC or HRB scale. MC602ST at 115–120 HRR is among the hardest unfilled nylons available. Higher tooth surface hardness reduces the indentation wear rate at the tooth contact zone, which is the primary plastic gear wear mechanism when running against a harder steel or nylon counter-gear.

Chemical Resistance

MC602ST nylon resists dilute acids, bases, alcohols, and most organic solvents that are common cleaning agents in food processing and pharmaceutical production environments. This chemical resistance, combined with the non-rusting property, makes MC602ST plastic spur gears with S45C steel cores the standard choice for gear drives in food processing equipment where the gear is periodically cleaned with CIP (clean-in-place) chemical agents.

Food Processing Machines

MC602ST / S45C steel core spur gears in conveyor drives, mixing machine drives, packaging machine mechanisms, and filling system actuators. No external lubrication required (food contamination risk eliminated). Chemical resistance to CIP agents. Steel core keyway withstands the moderate torque of conveyor drives without the plastic bore deformation that fails all-plastic gears.

Home Appliances

MC602ST steel core spur gears in washing machine drum drives, dishwasher spray arm drives, and refrigerator ice maker mechanisms. The steel core's bore stability across the thermal cycle of an appliance (0°C to 80°C in washers and dishwashers) eliminates the shaft fit loosening that all-plastic gears can experience after repeated thermal cycling. Quiet nylon teeth reduce appliance operating noise.

Chemical-Related Machines

MC602ST / stainless steel core spur gears in chemical metering pump drives, laboratory reagent dispensing systems, and pharmaceutical tablet compression machine drives. Stainless steel core specified where the hub bore is exposed to the process chemical — the nylon tooth body remains outside the chemical stream while the stainless core provides corrosion resistance at the shaft interface.

Toys and Consumer Products

MC nylon / S45C core spur gears in high-quality motorised toy drives and hobby equipment where the toy's gear train must withstand the shaft torque of a motor with a metal shaft — beyond the capability of an all-plastic bore at the motor shaft press fit. The steel core eliminates the bore splitting failure mode common in all-plastic gears on motor shafts at elevated torque.

Medical Equipment

MC602ST / stainless steel core spur gears in hospital bed electric positioning drives, rehabilitation equipment actuators, and medical imaging equipment table drives. The stainless steel core withstands the hospital's anti-corrosion cleaning cycle; the nylon teeth deliver quiet operation and no particulate generation from the gear mesh — a hygiene requirement in clinical environments.

General Industrial Drives

MC602ST / S45C core spur gears wherever plastic gear noise, corrosion, and lubrication advantages are required but the shaft keyway load or bore diameter exceeds what all-plastic gears can reliably carry. The steel core plastic spur gear bridges the gap between all-plastic and all-metal gear specifications at intermediate load levels.

Why are S45C steel hubs fused into nylon gears rather than bolted?

The two standard methods for attaching a steel hub to a nylon gear body are bolting and fusion. Bolting (using steel bolts through the nylon body into tapped holes in the steel hub) allows the gear to be disassembled for hub or nylon replacement — but the bolts add weight, require assembly labour, and create stress concentrations in the nylon at the bolt holes. When the bolts cannot be repaired (sealed gearboxes, permanently installed mechanisms), fusion is the preferred method. Korea Ever-Power's fusion process bonds the steel hub and nylon gear body such that the fused joint is stronger than the nylon teeth — the gear tooth will yield before the hub-nylon interface separates. This eliminates the risk of silent hub loosening that undetected bolt loosening can produce in service.

What is MC602ST and why is it preferred over standard PA6 for spur gear teeth?

MC602ST is an oil-impregnated monomer cast nylon — a high-density, low-residual-stress nylon produced by casting rather than injection moulding. Its mechanical properties exceed those of injection-moulded PA6: higher tensile strength, higher impact toughness, lower moisture absorption, and better surface hardness (115–120 HRR vs approximately 100–110 HRR for PA6). The oil impregnation (molybdenum disulfide or mineral oil) provides inherent lubrication at the tooth contact surface, extending the running life in lightly or unlubricated applications. For gear teeth that must run against a steel counter-gear in a food processing or chemical machine environment, MC602ST's combination of mechanical properties and lubricity makes it the preferred material.

Can a stainless steel hub be used instead of S45C for food or chemical applications?

Yes — stainless steel (typically SS304 or SS316L) hub inserts are available as an alternative to S45C steel hubs. The stainless core is specified when the hub bore is exposed to a corrosive process chemical or cleaning agent — the S45C steel hub can rust in chloride-containing environments if the nylon body is damaged and the hub surface is exposed. In food processing and pharmaceutical applications where the hub material must meet AISI 316L corrosion resistance requirements, the stainless steel hub is the standard specification. Specify the hub material grade on the drawing or at the order stage.

What is JIS Grade N9 (JIS B1702-1: 1998) for plastic gears?

JIS B1702-1: 1998 is the current Japanese standard for cylindrical gear accuracy, using the "N" grade system where lower N numbers indicate higher accuracy (N3 is the most accurate; N12 is the least accurate). JIS Grade N9 for plastic spur gears represents the achievable accuracy for moulded or machined plastic gears — it is the practical limit for spur gear tooth accuracy when the gear is produced from engineering thermoplastics with controlled process parameters. This corresponds approximately to DIN 9 or AGMA 9 in their respective national standards. The older JIS Grade 5 (JIS B1702: 1976) refers to the previous JIS standard using a different numbering system — the coexistence of both grade references on the specification table reflects that different customers' drawings may reference either standard.

Can plastic spur gears with steel cores be produced at modules other than M1?

Yes — Korea Ever-Power produces MC602ST / steel core spur gears at any module in the standard range. The NSU1-50 (Module 1, 50 teeth) is a standard catalogue example; other modules and tooth counts are produced to customer drawing. For modules above M2, the increased tooth height means the nylon body wall thickness between the tooth root and the steel hub insert increases — which can allow larger bore diameters relative to the hub diameter without reducing the wall thickness below the minimum for adequate tooth support. Contact Korea Ever-Power with the required module, tooth count, bore diameter, and hub diameter and we will confirm the feasibility of the specific geometry and the fusion bond specification. Contact our team with your drawing.

"We manufacture conveyor drives for food processing plants. Korea Ever-Power's MC602ST / S45C core spur gears M1 replaced our previous all-PA6 gears, which were failing at the keyway after 6 months of CIP cleaning cycles. The steel core keyway has been in service for 22 months with no bore loosening or keyway deformation. No external lubrication applied — the oil-impregnated MC602ST runs dry as designed."

Kim Hyeon-seok  |  Food Equipment Drive Engineer, Incheon Food Processing Equipment Co.  ·  Q1 2026

"We supply hospital bed positioning drives and use MC602ST / SS316L core spur gears from Korea Ever-Power. The stainless core resists the hospital's weekly chlorine disinfection; the nylon teeth produce below our operating noise limit. Korea Ever-Power's fusion process was confirmed by destructive testing of 3 samples from the first production batch — hub-nylon bond failed above the tooth root bending limit in all 3 samples, confirming the bond specification."

Lee Min-jeong  |  Medical Bed Mechanism Engineer, Gyeonggi Hospital Equipment Co.  ·  Q4 2025

"We design pharmaceutical dispensing machines and required MC602ST / SS316L steel core spur gears with FDA-compliant nylon material. Korea Ever-Power confirmed MC602ST's compliance with FDA 21 CFR 177.1500 (nylon resins food contact). Stainless steel core material certificate (SS316L) included with delivery. Fusion bond strength test report provided as requested."

Park Soo-yeon  |  Pharmaceutical Equipment Mechanism Engineer, Busan Pharma Equipment Co.  ·  Q2 2026

"We make high-quality motorised toy vehicles and switched from all-PA6 gears to MC602ST / S45C core spur gears from Korea Ever-Power after motor shaft bore splitting failures in returns. The steel core bore has eliminated the splitting failure mode entirely over 18 months of production. Tooth noise is lower than our previous POM all-plastic gears — MC602ST's oil impregnation reduces the tooth contact noise at the gear mesh frequency."

Choi Dong-seok  |  Toy Product Design Engineer, Daejeon Premium Toys Co.  ·  Q3 2025

"We import MC602ST / S45C core spur gears for distribution to home appliance manufacturers. The JIS N9 accuracy grade is confirmed on the dimensional inspection report provided with each batch. Korea Ever-Power supplies at a range of modules and tooth counts from a single order — efficient for our distributorship that carries a broad inventory of these gears for multiple appliance builder customers."

Yoon Hyeon-suk  |  Appliance Component Import Manager, Ulsan Home Appliance Parts Co.  ·  Q1 2025