Gears for Oil Pumps

Gears for oil pumps are precision-machined gear components used in gear-type hydraulic and lubrication oil pumps — one of the most common positive-displacement pump types in industrial and mobile hydraulic systems. The gear pump is valued for its simplicity, reliability, and ability to generate high pressure with low pulsation. Korea Ever-Power has focused on gear processing for 20 years, manufacturing oil pump gears in alloy steel, carbon steel, cast iron, aluminium alloy, stainless steel, copper, brass, and plastic — in modules M0.5 to M16, with heat treatment options including high-frequency quenching, hardening and tempering, carburising, flame hardening, and nitriding. Customised design and processing per customer drawing or sample.

Korea Ever-Power's oil pump gears offer: high-quality materials and professional production; strong and durable construction with ample torque capacity and good comprehensive mechanical properties; high rotation efficiency with stable and smooth transmission; long service life with noise reduction and shock absorption; carburised and quenched tooth surface for strong wear resistance, reliable operation, and high bearing capacity; and ground tooth surface option for highest precision.

External Gear Pump Principle

An external gear pump uses two meshing external spur gears — a drive gear and an idler gear — rotating in opposite directions inside a housing with close clearances. Fluid enters at the inlet port (on the unloading side of the mesh), fills the tooth spaces of both gears, and is carried around the outside of each gear to the outlet port (on the pressure side of the mesh). At the mesh point, the teeth engage and displace the fluid to the outlet, generating flow and pressure. The flow rate per revolution is determined by the tooth volume displacement — gear OD × face width × tooth depth × number of teeth.

Internal Gear Pump Principle

An internal gear pump uses a small external spur gear (the inner gear / rotor) meshing with a larger internal ring gear (the outer gear / stator) that has one more tooth than the inner gear. The eccentric meshing creates expanding and contracting fluid chambers as the gears rotate — the expanding chambers create the inlet flow and the contracting chambers create the outlet pressure. Internal gear pumps are compact, produce lower pulsation than external gear pumps, and can handle higher-viscosity fluids — making them common in engine lubrication circuits, gearbox lubrication, and hydraulic systems requiring low noise.

OD-to-Bore Concentricity — Volumetric Efficiency

The radial clearance between the gear OD and the pump housing bore is the primary determinant of the pump's volumetric efficiency (ratio of actual flow to theoretical flow). This clearance — typically 0.02–0.05 mm on precision pump gears — controls the internal leakage from the high-pressure outlet side back to the low-pressure inlet. Any eccentricity between the gear OD and the bore causes the effective clearance to vary around the circumference, increasing average leakage and reducing volumetric efficiency. Korea Ever-Power's grinding capability achieves the OD-to-bore concentricity required for high-efficiency pump gears.

Tooth Form Accuracy — Pressure Pulsation

Pressure pulsation in gear pump output is caused by the variation in displacement volume as successive teeth engage and disengage. Perfect involute tooth geometry produces minimum pulsation by ensuring constant velocity ratio during tooth engagement. Tooth profile errors — pitch error, profile form error, tooth-to-tooth spacing error — all cause departure from constant velocity ratio and increase pulsation amplitude. Ground tooth surfaces (gear shaving → honing → grinding) progressively reduce these errors, reducing pulsation and the associated hydraulic noise in sensitive applications.

Face Width Flatness — End Face Leakage

The axial clearance between the gear face width and the pump housing end plates determines the end-face leakage — the second leakage path in a gear pump. The gear faces must be flat, parallel, and within the specified face width tolerance (typically ±0.01 mm for precision pump gears) to achieve the designed axial clearance of 0.02–0.04 mm that limits end-face leakage to acceptable levels. Korea Ever-Power's grinding capability on gear face surfaces meets these flatness and parallelism requirements.

Material and Hardness for Pump Service

Oil pump gear material selection depends on the fluid type, operating pressure, and speed. Steel alloy gears (carburised, HRC 58–62) for high-pressure industrial hydraulic pumps. Cast iron gears for lower-pressure, slower-speed lubrication pumps where the cast iron's porosity holds lubricant and the material's damping reduces pulsation noise. Stainless steel for corrosive fluid pumps (fuel, water-glycol hydraulic fluids). Brass and copper for oil pumps handling fluids that are corrosive to carbon steel. Aluminium alloy for lightweight low-pressure pumps in automotive and aerospace applications.

① High-Quality Materials and Precision Equipment

High-quality materials selected from the full range — alloy steel, carbon steel, cast iron, aluminium alloy, stainless steel, copper, brass, and plastic — matched to the specific oil pump application's fluid, pressure, speed, and corrosion environment. Professional gear processing equipment: gear hobbing, shaping, milling, shaving, honing, and grinding machines. Customised design and processing adapts the gear geometry to the specific pump housing for optimal volumetric efficiency.

② Strong, Durable, High Torque Capacity

Korea Ever-Power's oil pump gears are strong and durable — with muscular tooth root bending strength to resist the high contact force between meshing pump gear teeth under maximum pressure. Ample torque capacity ensures the gear set transmits the drive torque required at the pump's maximum rated pressure without tooth root fatigue failure. Good comprehensive mechanical properties (hardness, toughness, fatigue strength) are verified by heat treatment control and hardness testing.

③ High Rotation Efficiency, Stable Transmission

High rotation efficiency — minimum friction losses in the gear mesh — means more of the drive shaft power reaches the fluid as hydraulic power. Stable and smooth transmission (accurate tooth form, correct centre distance, proper backlash) minimises pulsation in the gear pump's pressure output, reducing hydraulic system noise and pressure ripple. Long service life from wear-resistant tooth surfaces and correct lubrication design.

④ 20 Years of Gear Processing Focus

Korea Ever-Power has focused on gear processing for 20 years — accumulating the process knowledge, tooling investment, and quality system experience that produces consistent oil pump gear quality across all material types and module ranges (M0.5–M16). This 20-year focus on gear processing means Korea Ever-Power's engineers understand the specific requirements of pump gears — OD concentricity, face flatness, tooth form accuracy, backlash control — that distinguish pump gears from general transmission gears.

⑤ Carburised and Quenched Tooth Surface

Carburising and quenching of the tooth surface (case HRC 58–62) gives strong wear resistance — the primary surface treatment for high-pressure, high-speed hydraulic pump gears in alloy steel. The hard case resists the abrasive wear from fluid contamination particles and the adhesive wear (scuffing) from momentary lubricant film failure under high pressure. Reliable operation and high bearing capacity result from this combination of hard surface and tough core — the tooth can withstand the impact of contamination particles without brittle fracture while resisting surface wear.

⑥ Ground Tooth Surface — Highest Precision

The tooth surface can be ground after heat treatment, achieving the highest precision level for the most demanding pump applications. Gear grinding after carburising and quenching corrects the small distortions that heat treatment causes in the tooth form and OD, producing gear tooth accuracy approaching DIN 4–5 — the standard for the highest-quality hydraulic pump gears used in pressure-compensated pumps, servo-controlled hydraulic systems, and precision machine tool hydraulic circuits where pressure pulsation and noise are tightly controlled.

Industrial Hydraulic Power Units

External gear pump gear sets for industrial hydraulic power units supplying press, injection moulding, and metalworking machine hydraulic circuits. Operating pressures 100–300 bar, speeds 1,000–3,000 RPM, flows 10–200 L/min. Korea Ever-Power's M2–M6 alloy steel carburised gear sets cover the full range of industrial hydraulic pump sizes, with ground tooth surface option for the lowest noise in machine tool applications.

Automotive Engine Oil Pumps

Internal gear pump (gerotor) rotor and stator gear components for automotive engine oil pumps. Engine oil pump gears operate at very high speed (up to 8,000 RPM at engine speed), must resist wear from cold-start conditions when the oil film is thin, and must maintain tight clearances over a wide temperature range (−30°C to +150°C oil temperature). Material: alloy steel or powder metal (sintered), nitrided or carburised. Korea Ever-Power's M0.5–M2 fine-pitch capability covers automotive oil pump rotor geometries.

Agricultural and Construction Equipment

External gear pump gear sets for agricultural tractor hydraulic systems (three-point linkage, remote outlets, power steering) and construction equipment hydraulic circuits (excavator, loader, crane). These pumps operate in contaminated environments — the gear material and tooth surface hardness must resist abrasive wear from particles that enter with return line oil contamination. Korea Ever-Power's carburised alloy steel gear sets (HRC 58–62) provide the wear resistance needed in these demanding environments.

Lubrication Oil Systems

Internal gear pump (crescent pump) gear components for industrial gearbox lubrication oil circuits, compressor lubrication systems, and turbine bearing oil supply systems. Lubrication oil pump gears typically operate at lower pressure (2–20 bar) and higher viscosity fluid than hydraulic pump gears — cast iron or nodular cast iron gear sets are common at these conditions, offering good wear resistance in oil, easy manufacture of the complex internal gear geometry, and good damping of pressure pulsation.

Chemical and Process Industry Pumps

Stainless steel, brass, or copper gear sets for chemical process gear pumps handling corrosive fluids, specialty chemical metering, polymer melt transfer, and food-grade oil pump applications. Korea Ever-Power's stainless steel (304, 316) and copper alloy gear production covers these corrosion-resistant pump gear requirements, with smooth ground tooth surfaces for accurate metering and minimum fluid contamination from gear wear particles.

Aerospace and Defence

Lightweight aluminium alloy or high-strength alloy steel gear sets for aircraft hydraulic system gear pumps and military vehicle hydraulic system pumps. Aerospace pump gears require the tightest dimensional tolerances, highest material quality documentation, and surface finish (Ra ≤ 0.4 µm) of any pump gear application — Korea Ever-Power's gear grinding capability achieves these requirements for aerospace-grade oil pump gear production.

Are you a trading company or a manufacturer?

Korea Ever-Power is a factory — a direct manufacturer with 20 years of gear processing experience. This means factory-direct pricing, direct engineering support for pump gear design and OD/bore concentricity specification, and direct quality control accountability. No intermediary mark-up; no communication delays through a trading company layer.

What delivery time should I expect?

If the goods are in stock: 5–10 days. If the goods are not in stock and production is required: 15–20 days depending on quantity. For custom oil pump gears produced per customer drawing or sample, the 15–20 day lead time applies — this covers material procurement, gear cutting, heat treatment, grinding (if specified), and quality inspection.

What information is needed to quote oil pump gears?

Provide: gear type (external spur or internal gear pump), module (M0.5–M16), number of teeth (both gears for external pump; rotor/stator tooth counts for internal pump), face width, bore diameter and tolerance, OD diameter and concentricity requirement, material, heat treatment, and required surface finish. If a drawing (DWG, STEP, PDF) is available, send it directly. If no drawing is available, send a sample gear — Korea Ever-Power can measure and quote from the sample. Contact Korea Ever-Power today.

"We manufacture industrial hydraulic power units and source external gear pump gear sets from Korea Ever-Power — M4, 20CrMnTi carburised, ground tooth. OD-to-bore concentricity measured on CMM: 0.012 mm — well within our 0.025 mm spec. Pump volumetric efficiency on test bench at 200 bar: 94.2% — 1.8% higher than previous supplier at same speed. Pressure pulsation peak-to-peak: 4.1 bar — within our 5 bar limit. Delivery: 17 days for 200 gear sets. Price 14% lower than previous domestic source."

Kim Byeong-seon  |  Hydraulic Power Unit Production Manager, Incheon Hydraulics Co.  ·  Q2 2026

"We produce stainless steel gear pumps for food-grade oil metering in the food processing industry and source SS316 gear sets from Korea Ever-Power. Surface finish Ra 0.4 µm confirmed on profilometer — meeting our food contact surface spec. No dimensional rejects in 6 batches (120 gear sets). Free sample supplied for initial validation; sample geometry matched drawing dimensions within ±0.008 mm on all critical features. Korea Ever-Power's 20 years of gear processing experience shows in the consistent quality across batches."

Lee Won-jun  |  Food Processing Equipment Engineer, Gyeonggi Food Systems Co.  ·  Q4 2025