Tractor Spur Gears

Tractor spur gears are precision-machined steel gear components used in the transmission systems of agricultural tractors. They can change speed and torque, the direction of motion, and the form of motion — the fundamental functions of all mechanical gear transmissions. Korea Ever-Power's tractor spur gears are characterised by high transmission efficiency, accurate transmission ratio, and extensive power range, making them suitable for all classes of agricultural tractor from compact utility models to large four-wheel-drive field tractors. The standard product is a tractor spur gear with 17 teeth (OEM reference 50-1701212A), dimensions 5 cm × 9 cm × 9 cm, weight 0.87 kg, material: steel.

Korea Ever-Power's tractor spur gears are produced using professional CAD/CAM software and qualified engineers to design products with optimised dimensions and performance. Materials are selected based on different strength and performance requirements, choosing steel with firm compression resistance for each application. Customisation available per customer OEM drawing or sample. MOQ: 30 pieces. Packaging: carton. Quality: 100% tested before shipment.

Changing Speed and Torque

The transmission ratio i = Z₂ / Z₁ (driven / driving gear teeth) determines the speed reduction and torque multiplication between the input and output shafts. A 17-tooth tractor spur gear driving a 34-tooth gear produces 2:1 speed reduction and 2:1 torque multiplication (minus friction losses). Tractor transmissions combine multiple such gear pairs in sequence, providing a range of overall ratios from fast field transport (3–4 km/h) to PTO-matched field working speeds (5–10 km/h) to very slow precision seedbed speeds (under 1 km/h).

Changing Direction of Motion

Two meshing external spur gears rotate in opposite directions — the driven gear turns opposite to the driving gear. A tractor reverse gear is achieved by inserting an additional "idler" spur gear between the input and output gears: the idler reverses the direction of rotation without changing the ratio (idler tooth count cancels out). Tractor reverse gear assemblies typically use this idler gear principle, providing reverse motion at a ratio similar to first or second forward gear.

Changing Form of Motion

When a spur gear (pinion) meshes with a linear gear rack, the rotary motion of the spur gear is converted to the linear motion of the rack — or vice versa. In tractor applications, this rack-and-pinion arrangement appears in the tractor's steering system (converting the rotary motion of the steering box output shaft to the linear motion of the drag link or steering rack) and in some tractor three-point linkage depth control mechanisms.

High Transmission Efficiency

Spur gear mesh efficiency is typically 98–99.5% per gear pair — the highest of any gear type for parallel-shaft drives. This high efficiency means that 98–99.5% of the engine power passing through each spur gear pair reaches the output shaft; only 0.5–2% is lost to tooth friction and splash lubrication losses. In a tractor with 3–5 gear pairs in the power path, total transmission efficiency is typically 93–97% — significantly more of the engine's power reaches the drive wheels than with chain or belt drive alternatives.

Accurate Transmission Ratio

Unlike belt or chain drives, spur gear transmissions have an exact, constant, integer transmission ratio — determined precisely by the tooth count ratio. The ratio does not vary with belt slip or chain elongation; it is constant from the first revolution to the ten-millionth revolution. For GPS-guided precision agriculture, where the tractor's actual ground speed must be known accurately to control seed or fertiliser application rates, this exact gear ratio relationship is essential — the drive wheel rotation count gives the exact distance travelled.

Extensive Power Range

Steel spur gears can transmit power from fractions of a watt (miniature instrument drives) to thousands of kilowatts (large industrial drives) — with the power capacity scaling with the square of the gear diameter and linearly with face width at constant module. Tractor spur gears in the 9 cm diameter range transmit 20–100 kW at the tractor's rated engine speed — a power density achievable because of the compact, direct tooth-to-tooth force path in spur gearing.

① Material Selection

According to the different strength and performance requirements of each tractor gear position, Korea Ever-Power selects steel with firm compression resistance — typically 20CrMnTi for carburised case-hardened gears, 40Cr for induction-hardened gears, or 45# for moderate-duty normalised and quenched-and-tempered gears. Material selection is documented and the material certification (chemical composition, mechanical properties) supplied with each batch.

② Professional Design with CAD/CAM

Professional engineers use CAD software to design tractor spur gear dimensions with optimised size and performance. The gear tooth profile, undercut clearance, tip relief, and root fillet geometry are all optimised for the specific tractor application — ensuring correct mesh contact ratio, acceptable backlash, and adequate tooth root strength at the required torque level. CAM programs translate the design directly to CNC machine tool paths for consistent production accuracy.

③ Customisation per OEM Requirement

Korea Ever-Power can customise tractor spur gears to optimise performance under different working conditions — adjusting tooth count, module, face width, bore diameter, keyway dimensions, and surface treatment to match the customer's specific tractor model and transmission position. The optimal performance of the gear is exerted under each specific working condition through this customisation process.

④ Quality Assurance — 100% Tested

Quality assurance at every production step ensures product quality is controllable — from raw material inspection through gear cutting, heat treatment, and final dimensional and surface inspection. Every tractor spur gear is 100% tested before shipment: dimensional check of OD, bore, face width, tooth thickness, and runout; visual inspection for surface defects; and hardness verification to confirm heat treatment was correct.

Tractor Main Transmission

17-tooth (and other tooth-count) spur gear sets in tractor main transmission layshaft and mainshaft gear clusters. The standard 17-tooth gear (OEM 50-1701212A, diameter 9 cm) is a common layshaft gear in Chinese-made tractor transmissions used in the domestic and international agricultural equipment market. OEM and aftermarket replacement supply available.

Range Change and Hi-Lo Section

Spur gear pairs in the tractor's range-change section (high/low range selection) providing the two-ratio range multiplication that doubles the number of effective gears available. Range-change spur gears are large-module (M6–M10) since they carry the full transmitted torque at the relatively low shaft speeds of the range section input shaft.

PTO Gear Trains

Spur gear pairs in tractor PTO gear trains driving the PTO shaft at the standard 540 RPM or 1,000 RPM speeds from the engine's rated speed. PTO gear trains require precise tooth count ratios to achieve the exact PTO speed required — the exact transmission ratio of spur gearing makes tooth count selection the precise tool for achieving standard PTO speeds from any engine speed.

Hydraulic Pump Drive

Small-module (M2–M4) precision spur gears in the tractor hydraulic pump drive gear train. The hydraulic pump must rotate at a specific speed for the correct oil flow volume — achieved by the precision tooth count ratio of the pump drive spur gears. These are high-speed, continuously-running gears requiring ground tooth flanks for low noise in the tractor cab at all engine speeds.

Agricultural Implement Drives

Spur gears in tractor-mounted implement drives — rotary cultivator gearboxes, seed drill metering gearboxes, and fertiliser spreader rate-change drives that use the tractor PTO or wheel-speed output. These implement spur gears must be replaceable as service wear items during the implement's working life, making standardised tooth count and OEM reference number identification essential for aftermarket replacement supply.

Reverse Idler Gear

The reverse gear idler — an additional spur gear inserted between the layshaft and mainshaft gears to reverse the output rotation direction for reverse vehicle motion. The reverse idler gear must have a wide face width to span the axial gap between the layshaft and mainshaft gears, and must be mounted on a floating shaft that allows it to slide in and out of engagement. Korea Ever-Power manufactures reverse idler spur gears to OEM specification for all common tractor transmission types.

What is the OEM reference number for the standard 17-tooth tractor spur gear?

The standard Korea Ever-Power 17-tooth tractor spur gear has OEM reference 50-1701212A. Dimensions: 5 cm × 9 cm × 9 cm, diameter 9 cm, weight 0.87 kg. MOQ 30 pieces. For other tractor gear OEM references, provide the tractor model, gear position, and OEM part number — Korea Ever-Power will confirm availability from existing tooling or produce per sample.

Can Korea Ever-Power customise tractor spur gears to different tooth counts or dimensions?

Yes — Korea Ever-Power's tractor spur gear programme covers customised gear designs per customer OEM drawing or sample. Professional engineers use CAD/CAM software to design products with more reasonable size and better performance for specific working conditions. Customised configurations can optimise gear performance for the specific tractor model, transmission position, and operating condition where the gear will be used.

How is quality controlled in tractor spur gear production at Korea Ever-Power?

Korea Ever-Power implements quality assurance in every step of tractor spur gear production to ensure product quality is controllable: incoming material inspection → gear cutting dimensional check → heat treatment hardness verification → final inspection (OD, bore, face width, tooth thickness, runout, surface quality) → 100% test before shipment. No tractor spur gear leaves Korea Ever-Power's facility without passing this full inspection sequence. Contact Korea Ever-Power for a quotation.

"We distribute tractor transmission spare parts for the Korean agricultural equipment aftermarket and source 17-tooth tractor spur gears (OEM 50-1701212A) from Korea Ever-Power. Dimensions confirmed: 9 cm OD, 5 cm face width — matches original part. Hardness check: HRC 58 at tooth surface — within carburised spec. MOQ of 30 pieces fits our initial stock requirement. 100% tested confirmation on each delivery note accepted by our QC department."

Kim Seung-min  |  Agricultural Spare Parts Distribution Manager, Incheon Agri Parts Co.  ·  Q2 2026

"We manufacture compact tractor PTO gearboxes and source custom spur gear sets from Korea Ever-Power per our drawings. CAD optimisation suggested by Korea Ever-Power engineering team increased face width by 4 mm at no cost increase — extending calculated fatigue life by 35%. First article inspection with full dimensional report supplied. Tolerance on bore diameter: ±0.015 mm — within our H7 fit requirement. Production since Q3 2025, zero failures reported."

Lee Hyeon-jun  |  PTO Gearbox Engineer, Gyeonggi Agricultural Machinery Co.  ·  Q1 2026