Customized Double Helical Gear – OD 100-5000mm, OEM Design

Customized double helical gears from Korea Ever-Power cover the full size range from 100 mm to 5,000 mm outer diameter — the broadest capability available in this product family. A double helical gear overcomes the axial thrust problem of single helical gears by using a double set of teeth slanted in opposite directions. A double helical gear can be considered as two mirrored helical gears mounted closely on a common axle: each half thrusts in the opposite direction, resulting in a net axial force of zero. This arrangement also removes the need for thrust bearings, reducing gearbox complexity and cost.

Korea Ever-Power's customised double helical gears are manufactured to the customer's drawing or sample in cast iron, carbon steel, alloy steel, and bronze. Pressure angle 14.5°–20°, center bore, straight or spiral tooth form. OEM brand name marking service. In-house R&D department for customers who need design support. Free samples from stock for evaluation; 3–5 day sample delivery time. Korea Ever-Power's double helical gears have been best-selling domestically and internationally through long-term development, obtaining numerous merchant approvals.

Smooth Operation

The double helical tooth form combines the progressive engagement of helical teeth with the load-sharing across two opposite-hand tooth sets. The result is the smoothest torque transmission achievable in an external parallel-shaft gear arrangement — ideal for drives where vibration transmission to the machine structure must be minimised.

High Strength in Tooth Contact

The higher effective contact ratio of the double helical form distributes the transmitted load across more tooth pairs simultaneously, reducing the peak Hertzian contact stress at each individual tooth pair. This translates directly to longer tooth surface fatigue life and higher permissible continuous torque compared with single helical gears of equal pitch diameter.

Elimination of Sideways Force

Each helical half of the double helical gear generates an axial (sideways) thrust in the opposite direction to the other half. When the gear is correctly assembled with center planes aligned, these forces cancel exactly — the net axial force on the shaft bearings and housing is zero. This distinguishes double helical gears from single helical gears and is the primary engineering reason for specifying the herringbone form in large drives.

Fully Balanced Thrust Load

With the axial thrust fully balanced, the bearing arrangement needs to accommodate only the radial gear load and external machine loads — not an additional axial gear thrust component. This allows smaller, lighter, and less expensive bearing selections and simplifies the housing design particularly in large customised gears where thrust bearing provision for a single helical gear would be costly and mechanically complex.

Lower Load on Gear Housing

Elimination of axial thrust directly reduces the bending moment and axial preload on the gear housing. For large customised gears in the 1,000–5,000 mm OD range, the housing design is significantly simplified when axial thrust is absent — wall thicknesses, fastener sizes, and housing stiffness requirements are all reduced compared with a single helical gear design of equivalent power.

Excellent Torque Transfer at High Speed

Double helical gears deliver excellent and smooth transfer of torque and motion at high rotational velocities — the large face overlap from the absence of axial thrust (herringbone gears can use wider face widths than single helical gears without increasing housing complexity) provides high contact ratio even at large pitch circle diameters where the tooth engagement cycle frequency is high.

Cast Iron

Suitable for large, low-speed drives where the gearbox can accommodate a larger, heavier gear to reduce cost. Cast iron double helical gears are the most economical option for very large OD configurations (above approximately 1,500 mm) where the casting process makes the blank cost significantly lower than forging. Good vibration damping. Limited to moderate tooth surface hardness levels.

Carbon Steel

45# carbon steel is the standard material for medium-load customised double helical gears across the full OD range. Through-hardening or surface hardening to the required hardness. Good machinability, good weldability for large fabricated blanks where a single casting or forging exceeds press capacity. The most widely used material in this product category.

Alloy Steel

40Cr, 42CrMo, 40CrNiMoA, and other alloy grades for high-load customised double helical gears. Higher hardenability allows deeper case hardening or higher through-hardened surface hardness than carbon steel — the correct specification for drives with high contact stress requiring long gear service life. Material selected per the application load and hardness requirement.

Bronze

Bronze double helical gears for drives requiring self-lubrication, corrosion resistance, or non-sparking properties — typically where one gear in the pair is bronze running against a steel pinion. Marine drives, chemical equipment, and fuel-adjacent applications. The 14.5° pressure angle option is particularly applicable to bronze gears, which are weaker in bending than steel and benefit from the shallower pressure angle's more tangential force vector.

Mining — Cement and Ball Mills

Large ring gears for cement mill and ball mill main drives in the 2,000–5,000 mm OD range. Cast iron or cast steel for the very largest configurations; alloy steel for higher load capacity. The herringbone form is standard in these drives because it allows a wider face width (more load capacity) without housing axial thrust complications.

Rolling Mill Main Drives

Customised alloy steel double helical gears for rolling mill main drive gearboxes and pinion stands across all rolling mill types. The wide OD range (100–5,000 mm) covers pinion gears at the small end through bull gears at the large end of heavy rolling mill main drives.

Naval Propulsion

Main reduction gear wheel sets for naval vessels — alloy steel customised double helical gears in the 500–2,000 mm OD range. Bronze pinions paired with steel wheels for the self-lubricating, corrosion-resistant naval standard where one member of each gear pair is bronze.

Large Industrial Cranes

Custom hoisting gearbox gear sets for very large overhead cranes, shipyard gantry cranes, and port container cranes where standard off-the-shelf gear sets are not available and bespoke manufacturing is required to match the existing housing and shaft arrangement.

Offshore and Energy

Wind turbine main gearbox stages, offshore jack-up platform elevation drives, and tidal turbine reduction gears — customised alloy steel double helical gears where the drive must operate at sea, at altitude, or in environments with limited maintenance access and high duty cycles.

Replacement and MRO

Single-unit replacement gears for any of the above applications where OEM spares are unavailable or priced at a premium. Korea Ever-Power's reverse engineering capability and OEM marking service makes it possible to produce a replacement that matches the original gear exactly — including the original manufacturer's branding if required.

Can OEM brand name marking be applied to customised double helical gears?

Yes — Korea Ever-Power provides OEM service for customer brand name marking on all customised double helical gears. Specify the required marking format (engraved, stamped, or laser marked), location (gear web, hub face, or bore), and the text or logo in the order documentation. OEM marking is frequently used by equipment builders who supply gears as part of branded gearbox assemblies, and by distributors who carry replacement gears under their own trade name.

Is Korea Ever-Power a manufacturer or trading company?

Korea Ever-Power is a manufacturer, not a trading company — production is carried out at the manufacturing facility in Zhejiang, China, with an additional office in Singapore. As a direct manufacturer, Korea Ever-Power controls the complete production process for customised double helical gears and can respond directly to technical questions about material, process, and quality without reference to a third-party supplier.

Can Korea Ever-Power provide gear design service?

Yes — the in-house R&D department accepts design commissions. Provide the application data (required ratio, input speed, rated torque, centre distance, shaft diameter, material preference, and operating environment) and the R&D team will produce a gear geometry proposal and drawing for customer approval before production begins. This service is particularly valuable for replacement gears where the OEM drawing is unavailable, or for new gearbox designs where the customer has the application specification but not the gear geometry.

Are free samples available, and how quickly can they be delivered?

Free samples are available from stock for standard configurations — delivery is approximately 3–5 days when the item is in stock. For customised configurations that are not in stock, a paid sample must be produced (lead time depends on configuration; confirm at enquiry stage). The free sample service is primarily for customers evaluating standard configurations before placing a production order; the paid sample service applies to fully customised configurations.

What shipping options are available for large customised double helical gears?

For small orders, Korea Ever-Power ships by UPS, DHL, FedEx, TNT, or EMS express — a tracking number is provided after delivery. For large customised gears that exceed the weight or size limits of express carriers, or where multiple large gears are ordered in a batch, air freight or sea freight is recommended. For very large gears (above approximately 500 mm OD), sea freight in a wooden crate is the standard shipping method; the crate design protects the tooth flanks from impact and fretting during the long sea transit. Contact our team with your gear size and delivery port and we will confirm the recommended shipping method and cost.

"We needed a 3,200 mm OD cast steel double helical bull gear for a cement mill main drive — a size that most gear suppliers cannot produce. Korea Ever-Power confirmed production capability, provided the R&D design service to adapt our torque and speed specification into the correct gear geometry, and delivered within the agreed timeline. OEM marking was applied per our specification."

Kim Cheol-min  |  Chief Engineer, Incheon Cement Plant Engineering  ·  Q1 2026

"We supply replacement gear sets to offshore energy clients and required custom alloy steel double helical gears at 850 mm OD with OEM markings matching the original manufacturer. Korea Ever-Power produced to our reverse-engineered drawing with the original brand marking as specified. Sea freight in wooden crate — gear arrived with no transport damage. The elimination of sideways force was confirmed in our bearing load calculation after installation."

Lee Sang-wook  |  Gear Supply Manager, Busan Offshore Equipment Supply Co.  ·  Q4 2025

"We manufacture naval auxiliary drives with bronze pinions running against alloy steel wheels in the double helical configuration. Korea Ever-Power produces both the bronze pinion and the steel wheel at the correct pressure angle (14.5° for the bronze-on-steel arrangement) and provides material certificates for both. The non-sparking bronze pinion is a classification society requirement for this fuel-adjacent application."

Park Jun-young  |  Marine Gearbox Design Engineer, Gyeongnam Naval Equipment Co.  ·  Q2 2026

"We build very large overhead cranes for shipyard use and needed a 1,600 mm OD alloy steel hoisting gearbox bull gear — a size our domestic suppliers cannot turn around on an emergency basis. Korea Ever-Power delivered in the required window with OEM marking. The R&D service produced the drawing from our application specification in 8 working days, which is remarkably fast for this gear size."

Choi Byeong-hun  |  Lifting Equipment Lead Engineer, Ulsan Crane Manufacturing  ·  Q3 2025

"We import and wholesale customised double helical gears up to 2,000 mm OD for the heavy industry MRO market. Korea Ever-Power's combination of OEM marking service, Singapore office (for regional logistics coordination), and direct manufacturer pricing makes them the right partner for this product range. Best-selling product in our heavy gear portfolio for 3 consecutive years."

Yoon Sang-ho  |  Wholesale Import Director, Seoul Heavy Industrial Components  ·  Q1 2025