How to Read a Worm Gear Reducer Datasheet: Every Parameter

Every worm gear reducer datasheet lists the rated output torque, the efficiency, the thermal power rating, the input speed range, and a dozen other numbers. What the datasheet rarely lists — unless you know to look for it — are the test conditions under which each number was measured.

Rated torque T₂n is measured at 20°C ambient, rated input speed, full load, continuous S1 duty, standard mineral oil, at operating temperature equilibrium. Change any one of those conditions and the actual achievable torque changes. The same T₂n figure applies to an application at 35°C ambient with 16-hour duty — but the unit will fail prematurely if you use T₂n directly without accounting for those conditions.

This guide explains the actual engineering meaning of 15 datasheet parameters, the conditions that qualify each one, and the common misinterpretation that leads to selection errors. By the end, you can read any worm gear reducer datasheet and immediately identify which numbers require correction factors for your application.

1. T₂n — Rated Output Torque

Definition: The maximum continuous output torque the unit can deliver under standard test conditions: S1 continuous duty, rated input speed, 20°C ambient, standard mineral oil at operating temperature.

Common misuse: Treating T₂n as the maximum safe torque for any operating condition. It is the standard condition rating — your application torque multiplied by SF must be ≤ T₂n.

Correct use: T₂n ≥ T_application × SF. Never compare raw application torque to T₂n without service factor.

2. T₂max — Maximum Output Torque

Definition: The peak torque the worm gear reducer can withstand for short durations — typically ≤3 seconds, no more than a few times per hour. T₂max is typically 2.0–2.5× T₂n.

Common misuse: Selecting a worm gear reducer where the rated application torque approaches T₂max. This leaves no margin for transient overloads.

Correct use: T₂max sets the upper limit for infrequent short-duration peaks (stall, jam, emergency). Continuous torque must stay well below T₂n × (1/SF).

3. P_th — Thermal Power Rating

Definition: The maximum continuous input power at which the housing temperature stabilizes below the maximum allowable level under standard conditions (20°C ambient, still air, horizontal mounting).

Why it matters more than you think: For large ratios (40:1+), P_th is often lower than the mechanical P_mech. The thermal limit — not the gear teeth — is often what constrains continuous-duty operation.

Common misuse: Using P_th at face value without ambient temperature correction. At 35°C ambient, P_th is only 80% of the catalog value.

4. η — Efficiency

Definition: The ratio of output power to input power, measured at full load, rated speed, operating temperature, with standard mineral oil. Varies significantly with ratio — ranges from ~88% at 7.5:1 to ~48% at 100:1.

Conditions affecting η: Cold oil reduces η at startup (higher viscosity, more churning loss). Partial load reduces η slightly below full-load value. High-quality bronze and precision-ground worm shaft achieve the upper end of the efficiency range.

Correct use: Use the lower value of the efficiency range for thermal power calculations; use the nominal value for output torque/power estimates.

5. n₁min / n₁max — Input Speed Range

Definition: n₁min is the minimum input speed at which the lubricant is adequately distributed across the gear mesh by splash and churning. Below n₁min, the gear mesh may run partially dry at startup or under low-speed operation.

n₁max is the maximum input speed before centrifugal effects reduce lubrication effectiveness, bearing heat generation exceeds the thermal balance, or the dynamic balance of the worm shaft becomes a concern.

Application note: VFD-controlled applications at very low speeds (below n₁min) require forced lubrication or a grease-lubricated variant — check with the manufacturer.

6. Fa₂ — Axial Force on Output Shaft

Definition: Maximum allowable axial (thrust) force on the output shaft, applied at the shaft centerline. Axial forces arise from helical coupling reactions, spring-loaded mechanisms, and thrust from the driven equipment.

Most neglected parameter: Engineers check Fr₂ (radial load) almost universally, but frequently overlook Fa₂. Axial overload on the output shaft bearing manifests as premature axial bearing wear and end-play development.

Critical applications: Screw conveyors, vertical agitators with buoyancy forces, and applications with spring-applied shaft forces all generate significant Fa₂.

7. Fr₂ — Radial Force on Output Shaft

Definition: Maximum allowable radial (transverse) force on the output shaft, typically stated at the midpoint of the shaft extension. This force comes from belt tension, chain tension, gear mesh force, or gravity overhang of connected components.

Distance matters: The Fr₂ in the datasheet usually assumes force applied at the center of the shaft extension. If the force is applied at the shaft end (maximum overhang), the allowable value is approximately 20–30% lower.

Exceeding Fr₂ does not cause immediate failure — it reduces output bearing L10h life disproportionately (life varies with the inverse cube of radial load).

8. L10h — Rated Bearing Life

Definition: The number of operating hours by which 90% of worm gear reducers of this model will survive without bearing fatigue failure, under rated load conditions. L10h is a statistical 90th-percentile figure — 10% of units fail before this point even under rated conditions.

Application correction: Actual L10h in your application = Catalog L10h × (Fr₂_catalog / Fr₂_actual)³ × (n₁_catalog / n₁_actual). Doubling the radial load reduces bearing life to one-eighth.

L10h is not the expected failure point — it is the 10% failure point. Median bearing life is typically 5× L10h.

9. T_max — Maximum Housing Surface Temperature

Definition: The maximum allowable housing surface temperature, typically 80–90°C depending on manufacturer and sealing specification. At this temperature: NBR seal lips begin to harden and lose elasticity; standard mineral oil begins to oxidize rapidly; bearing grease (if any) begins to break down.

How to use it: Measure housing surface temperature at the geometric center of the housing. The oil temperature inside is approximately 15–25°C higher than the housing surface — a 75°C surface means ~95°C oil temperature.

VITON seals extend the safe operating limit to approximately 100°C surface temperature.

10. Lp — Noise Level dB(A)

Test conditions: Typically measured at 1 metre distance, no-load or rated-load condition (specified by manufacturer), input speed per datasheet, mounted on a rigid test bench, free-field acoustic environment.

In practice: Installed noise differs from test noise. Rigid mounting to a metal frame transmits structure-borne noise that increases perceived sound level. Flexible anti-vibration mounts can reduce this. Load increases worm gear reducer noise slightly.

Worm gear reducers are inherently quieter than helical gear reducers at equivalent torque and ratio due to the sliding contact mesh — typically 5–10 dB(A) lower at the same input speed.

11. Mounting Position Code (M1–M6)

Meaning: Defines the orientation of the worm gear reducer during installation — which shaft points in which direction relative to gravity. The code drives two critical specifications: the oil volume required to correctly submerge the gear mesh, and which housing port must serve as the vent plug to be at the highest point.

M1 = standard horizontal mounting. M2/M3 = vertical output shaft (up or down). M4/M5 = vertical worm shaft (up or down). M6 = inverted. Each code specifies an oil volume that differs from M1 by 10–20%.

12. d₂ — Output Shaft Diameter (and Tolerance)

Definition: Nominal output shaft diameter in millimeters. The datasheet always specifies a tolerance class — typically h6 (shaft) which pairs with H7 (bore) in a transition or clearance fit for standard shaft-hub connections.

Why tolerance matters: A 30 mm shaft at h6 tolerance is 30.000 to 29.987 mm. A driven hub at H7 is 30.000 to 30.021 mm. The fit can be clearance or interference depending on actual dimensions — this determines how the coupling or sprocket seats and whether it can be driven on by hand or requires pressing.

Keyway dimensions (width × depth × length) are separately specified and must match the hub keyway exactly.

13. Flange / Foot Mounting Dimensions

Key dimensions: For IEC flange-mounted worm gear reducers: the locating diameter (spigot), the bolt hole circle diameter, and the bolt hole size. The locating diameter tolerance (typically j6 or k6 on the reducer, H7 on the motor) determines the radial accuracy of motor shaft-to-reducer bore alignment.

For foot mounting: The bolt hole pattern must match the machine base. Note whether the foot holes are slotted (allowing adjustment) or round (fixed position). Slotted holes simplify alignment; round holes provide more rigid clamping.

Request a 2D dimensional drawing rather than relying on catalog dimensions for any precision fit-up — catalog drawings are often simplified.

14. Oil Volume (by Mounting Position)

Definition: The volume of lubricant required to bring the oil level to the correct position for each mounting orientation. This is usually provided in the installation manual as a table keyed to mounting position code, not in the main datasheet.

Common problem: Units shipped from the factory are pre-filled for M1 orientation. If you change orientation without adjusting oil volume, the gear mesh may be under-oiled or the shaft seals may be over-pressurized.

Always confirm oil volume for your specific mounting position. If the installation manual doesn’t specify, contact the manufacturer.

15. IP Rating — First and Second Digits

First digit (solid particle protection): IP5x = dust-protected (limited ingress). IP6x = dust-tight (no ingress under test conditions).

Second digit (liquid ingress protection): IPx4 = splash from any direction. IPx5 = water jets. IPx6 = high-power water jets. IPx7 = immersion to 1 metre for 30 minutes.

Important caveat: IP ratings are tested under specific laboratory conditions — the actual protection in service depends on seal condition, installation orientation, and whether the test water temperature matches the service water temperature. IP ratings degrade as shaft seals age — a new IP65 unit may be effectively IP54 after 5 years of service in an abrasive environment without seal maintenance.

The standard worm gear reducer catalog datasheet is a starting point, not a complete specification. For engineering selection of a worm gear reducer — particularly for continuous duty, food industry, or custom applications — request these additional documents from any worm gear reducer supplier:

2D dimensional drawing: Confirm all shaft, keyway, flange, and mounting hole dimensions with tolerances. Catalog line drawings are often simplified and may not show all tapped holes or auxiliary ports.

Efficiency-ratio curve: For thermal calculations, the specific efficiency at your operating ratio is more accurate than a generic table value. Request the actual measured efficiency data for the model and ratio you are specifying.

Material certificate: For food, pharmaceutical, or export documentation requirements, request material certificates for the worm gear reducer housing alloy, worm shaft steel grade, and bronze wheel alloy. Korea Ever-Power provides these as standard on request.

P_th vs ambient temperature data: Rather than applying a generic correction factor, ask for the manufacturer’s published P_th correction values at 25, 30, 35, and 40°C ambient. These values vary slightly between manufacturers depending on housing fin design and surface area.