Parallel Axis Helical Gears – Steel, Custom Module & Ratio

Parallel axis helical gears are the most widely used gear type in industrial machinery, defined by two characteristics: the shafts of the driving and driven gear run parallel to each other, and the teeth are cut at a helix angle rather than parallel to the shaft axis. Unlike ordinary spur gears which engage simultaneously along the full tooth width — causing shock, vibration, noise, and unstable transmission — helical gear transmission is progressive: contact begins at one end of the tooth and moves across the face width as the gear rotates, so the load is transferred smoothly and continuously.

It should be clarified that helical gears are not simply a sub-type of spur gears — they are a distinct gear form with a different meshing geometry. Parallel axis helical gears mesh in the mode of two helical surfaces in rolling contact, distinguished from crossed-axis helical gears by the requirement that both axes run parallel. Ordinary spur gears mesh simultaneously along the full tooth width; helical gears are better than spur gears and can handle higher speeds and heavier loads with lower noise at the same centre distance.

① Good Meshing Performance

The meshing process between teeth of parallel axis helical gears is gradual — the force on each tooth is transferred from small to large and then from large to small during each engagement cycle. Helical gears are therefore suitable for high speed and heavy loads where spur gears would generate unacceptable noise and fatigue loading. The smooth force transition also reduces bearing loads compared with the impulse loading of spur gear engagement.

② Large Coincidence Degree

The increase in coincidence degree (contact ratio) increases the load-bearing capacity of the gear and extends its service life. The contact ratio of a helical gear pair is higher than an equivalent spur gear pair because the tooth contact extends diagonally across the face width, meaning multiple tooth pairs share the load simultaneously. The meshing time per tooth cycle is longer and the contact area is greater, which reduces the contact stress at any individual tooth flank and prolongs tooth life.

③ Compact Structure

The minimum number of teeth to avoid undercutting is smaller for helical gears than for spur gears at the same module and pressure angle. A smaller minimum tooth count enables more compact gear pair designs and allows higher reduction ratios within a given centre distance. The helical gear reducer built on this principle achieves small size and lightweight at ample transmission torque — particularly relevant in multi-stage gearboxes where each stage must fit within the available envelope.

General Industrial Machinery

Conveyors, mixers, extruders, compressors, and general-purpose reduction gearboxes. The most numerous application category for parallel axis helical gears — wherever a motor must drive a machine shaft at reduced speed and increased torque through a parallel-shaft arrangement.

Machine Tools

Spindle gearboxes, feed axis drives, and speed change mechanisms in CNC machining centres, lathes, and grinding machines. High-speed helical gears in spindle drives operate at pitch-line speeds above 40 m/s and require ground teeth to DIN 5 or 6 accuracy.

Semi-Conductor Industry

Wafer handling robots, photolithography stage drives, and inspection equipment require helical gears in cleanroom-compatible materials (aluminium, stainless, or engineering plastics) at high accuracy grades for smooth, low-vibration positioning.

Medical Equipment

Surgical robot drives, diagnostic imaging gantry actuators, and rehabilitation equipment. Stainless steel or POM helical gears at high accuracy grades, with passivation or biocompatibility documentation as required.

Solar Energy Equipment

Solar tracker azimuth and elevation drives, and CPV concentrator positioning systems. Helical gear reducers in solar tracking drives operate outdoors year-round with minimal maintenance access — sealed helical gearboxes in alloy steel or aluminium are the standard drive solution.

Automatic Controlling Machines

Packaging machinery, labelling systems, filling machines, and pick-and-place automation. Helical gear stages in servo-driven automation provide the positional accuracy and quiet operation demanded in continuous high-speed automated production lines.

Parking Systems

Automated multi-level parking system drive mechanisms — pallet elevation drives, lateral transfer units, and carousel rotation drives. Helical gear reducers provide the smooth, controlled motion and high cycle life required in automated parking systems operating continuously over multi-year service periods.

High-Speed Rail & Aviation

Traction motor reduction gears in high-speed rail vehicles and aviation auxiliary drive gearboxes. High accuracy grades, alloy steel with carburising and grinding, and full material traceability documentation are the standard specification for these critical transport applications.

Does your company have export qualifications?

Yes. Korea Ever-Power holds export qualifications for industrial gear products to international markets. We supply parallel axis helical gears and helical gear reducers to customers in Europe, North America, South Korea, Southeast Asia, and other regions. All products are produced and documented to the relevant international standard (ISO, DIN, AGMA, JIS, BS) as specified in the customer's purchase order.

Are products customised to client drawings, or are standard stock items available?

All Korea Ever-Power parallel axis helical gears are customised according to the client's drawing. There is no standard stock catalogue of finished gears — each order is produced to the specific module, tooth count, helix angle, material, heat treatment, accuracy grade, bore, and hub dimensions provided by the customer. This ensures the delivered gear matches the design intent rather than the nearest available stock item. Please send us your drawing to begin the quotation process.

What is the MOQ?

MOQ depends on the specific product configuration. Please send us the drawing and we will confirm the minimum order quantity for that specification. For evaluation before committing to a production order, a sample can be ordered first — see the sample FAQ below.

How much does a sample cost, and how is the sample fee handled?

Sample price ranges from $2 to $100 depending on the configuration. Sample express freight is paid by the customer. After the sample is confirmed and a production order is placed, the sample fee is refunded to the customer. This policy ensures samples are provided seriously — both the customer and Korea Ever-Power commit to the evaluation process before the refund is applied.

How can Korea Ever-Power provide fast delivery without holding finished stock?

Korea Ever-Power's manufacturing process, combined with a large inventory of tools, raw materials, and semi-finished blanks in the most common alloy grades and module ranges, allows production orders to begin immediately upon order confirmation without waiting for material procurement or tool preparation. The standard 25 business day lead time for bulk parallel axis helical gear orders reflects the actual production sequence — blanking, turning, hobbing, heat treatment, and finishing — not a queue time. Contact our team with your drawing and required delivery date and we will confirm feasibility.

"We specify M3 alloy steel parallel axis helical gears in DIN 7 for a conveyor gearbox that operates 24 hours a day. Korea Ever-Power supplies to our drawing; the first delivery came within the 25-day lead time and every subsequent batch has arrived on schedule. Dimensional reports have been consistent batch to batch. Three years of supply without a single nonconforming delivery."

Shin Jae-hun  |  Procurement Engineer, Incheon Industrial Automation  ·  Q1 2026

"We develop solar tracker drives and use M5 C45 steel parallel axis helical gears in a sealed reduction gearbox. Ever-Power produced to our drawing with Dacromet surface treatment for corrosion resistance. After two years of outdoor operation across 120 tracker units, no gear corrosion or dimensional failures have been reported."

Oh Min-jun  |  Drive Systems Lead, Jeollabuk Solar Engineering  ·  Q3 2025

"We manufacture automated parking systems and order M4 stainless helical gears from Korea Ever-Power for the wet-zone transfer carriage drives. Passivation certificate meets our corrosion protection requirement. The sample evaluation process — machined prototype before production, sample fee refunded on production order — was exactly the risk management we needed for a new gear configuration."

Jung Soo-min  |  Systems Engineer, Seoul Smart Parking Co.  ·  Q4 2025

"We source M2 aluminium parallel axis helical gears for wafer handling robot joints. The gears must be non-magnetic and cleanroom-compatible. Ever-Power produced in 6061 aluminium with hard anodising, with the bore concentricity within 0.01 mm on every part in the batch. Lead time consistently within 25 business days on five consecutive orders."

Kwon Dong-hyun  |  Component Engineer, Gyeonggi Semiconductor Equipment  ·  Q2 2025

"We build packaging automation systems and use M1.5 brass helical gears in the timing drive. Brass was specified for its self-lubricating properties in a sealed drive where re-lubrication access is not practical. Ever-Power supplied with DIN 8 accuracy and zinc surface finish. No gear-related issues across 18 months of three-shift production operation."

Park Young-chan  |  Mechanical Design Engineer, Busan Packaging Machinery  ·  Q1 2026