Specifying gears for conveyors, hoists, pallet stackers, and automated storage starts with the duty cycle: conveyors running 8-24 h per day under uniform load typically take a 1.25 service factor, while pallet lines with impact loading require 1.5 and heavy bulk-handling with direct-on-line motor starting push the figure to 1.75-2.0 [S8].
Five gear families dominate the field: spur, helical, bevel, worm, and rack-and-pinion. Each is constrained by shaft arrangement, ratio, efficiency, and noise, so the gear is chosen after, not before, the machine envelope and load profile are fixed [S2]. For an overview of where these drive elements sit in the wider drivetrain, see the reference page on industrial gear.
Spur gears: simple, parallel-shaft, cost-driven
Spur gears carry straight, parallel-to-shaft teeth and are the lowest-cost option for parallel-shaft drives in conveyors, packaging machinery, and general mechanical drives [S2]. Because tooth engagement is abrupt, peripheral speeds are usually held below roughly 10 m/s in noise-sensitive areas, and they are rarely specified above 20 m/s without acoustic enclosures [S1]. The trade-off is audible: at higher speeds, spur gears generate more noise and vibration than angled-tooth alternatives [S2].
Where floor space, low cost, and parallel shafts dominate the brief, spur is the default. Where smoothness or high speed is mandatory, helical replaces it without changing the shaft arrangement.
Helical gears: smooth, quiet, higher load capacity
Helical gears have teeth cut at an angle to the axis, so engagement is progressive and the contact ratio is higher than spur at the same module [S1]. This delivers smoother operation, lower noise, and stronger load-carrying capacity, making helical the workhorse in industrial gearboxes, compressors, conveyors, and heavy equipment transmissions [S2]. The penalty is an axial thrust force on the supporting bearings, which must be carried in the system design.
For material-handling lines running above 10 m/s, or anywhere the OEM noise budget is tight, helical is the default. The extra bearing load is a routine accommodation, not a disqualifier.
Bevel gears: right-angle shaft redirection
Bevel gears mesh on intersecting shafts, typically at 90 degrees, and are the standard choice when the drive must turn a corner between motor and conveyor head shaft, hoist gearbox, or differential input [S1]. When specifying a bevel gear, the critical inputs are shaft angle, gear ratio, torque, speed, tooth configuration (straight, spiral, or hypoid), and the envelope available for the unit [S2].
Spiral bevels handle higher speed and load than straight bevels at the cost of more complex manufacture; hypoid variants, common in automotive differentials, are occasionally seen in heavy material-handling axles but are not the typical first choice for industrial conveyors.
Worm gearboxes: shock-load and self-locking hoists
Worm gearboxes are widely used in the material-handling industry because the sliding contact absorbs shock loads, frequent start-stops, and extended daily run times better than many rolling-element mesh designs [S10]. For conveyors with high inertia loads, frequent reversals, or outdoor exposure, the applicable service factor rises to between 1.5 and 2.5, multiplied into the calculated torque from the manufacturer's rating tables [S10].
The mechanical advantage is self-locking under load, useful for vertical lifts and hoists where back-driving is unacceptable. The cost is lower efficiency (typically 30-90% depending on lead angle and material pairing) and heat generation under continuous duty, so thermal derating must be checked for hot or enclosed installations [S8][S10]. A focused look at the broader category of industrial reducers is in the reference page on material handling.
Rack-and-pinion: linear motion for stackers, cranes, and AS/RS
A gear rack is a straight, toothed bar that meshes with a pinion to convert rotation into linear motion, and is the backbone of pallet stackers, crane traversing drives, and vertical storage and retrieval systems [S4][S6]. The first spec point is load capacity: the rack rating must exceed the maximum expected payload with a defined safety margin, taking into account the weight and size of the objects being transported [S6][S7].
Second, pitch and module must match the mating pinion; a mismatched module is the most common field failure on retrofits [S3][S7]. Third, surface hardness drives longevity: induction-hardened or case-hardened racks with ground teeth run substantially longer in high-cycle duty than unhardened stock [S4]. Material-handling rack-and-pinion duty also leans on the wider storage and handling drivetrain context.
Service factor and duty class: the numbers that govern the spec
Service factor is not a marketing number. It is the multiplier applied to the calculated torque from the steady-state load, used to size the gearbox against peak and shock conditions [S8][S10]. For uniform conveyor loads with soft-start motor starting, the multiplier is 1.25; for moderate-shock pallet conveyors it is 1.5; for heavy bulk handling with direct-on-line motor starting it sits at 1.75-2.0 [S8].
Output torque is computed as effective drive pull (N) multiplied by the drive element radius (m), then multiplied by the service factor [S8]. For a side-by-side selection view, the following comparison lines up the five gear families against four decision criteria commonly applied in material-handling drivetrains.
Gear-type comparison for material handling
Below is a criteria-based comparison extracted from the 2026 vendor and engineering references [S2][S8][S10].
Best for low-cost conveyors and packaging.
Default for high-speed conveyors, compressors, and gearbox inputs.
Bevel (straight/spiral): intersecting shafts at 90 deg; efficiency 97-98%; moderate noise; service factor 1.0-1.5. Default where the motor must turn a corner into the head shaft.
Worm: crossed shafts, high ratio in one stage; efficiency 30-90% depending on lead; self-locking; service factor 1.5-2.5 [S10]. Default for hoists, lifts, and shock-loaded outdoor conveyors.
Rack-and-pinion: rotary-to-linear; efficiency 90-97% (rack-pin pair); system service factor follows the application table. Default for stackers, crane traverse, and vertical AS/RS lifts [S6].
Material, environment, and standards
Material selection drives gear strength, fatigue life, weight, and corrosion resistance; common pairings are hardened alloy steels (through-hardened or case-carburised) for industrial gearing, with stainless or coated options for washdown and corrosive environments [S1]. The bearing and lubrication envelope must be reviewed alongside the gear itself, especially in dusty or hot installations where thermal derating is often missed [S8].
For EU machinery projects the applicable framework is Regulation (EU) 2023/1230, which includes chains and removable mechanical transmission devices within its scope, with conformity obligations depending on how each component is classified and integrated [S3]. For guarding, replacement dimensions, and maintenance access, US pallet conveyor practice emphasises a matched chain-and-sprocket review rather than a single-component specification [S3].
For Australian conveyor installations, thermal derating in hot climates is the most common oversight in gearbox selection, and the same engineering source recommends applying a service factor multiplier on top of the steady-state torque rather than relying on a nameplate match [S8]. Comparable practice is documented for the mining and steel-mill duty classes, where service factor, sealing, and steel grade interact in the selection decision; a focused look at adjacent drivetrain duty is in the steel mill gearbox spec map, and helical/bevel/planetary trade-offs in mining are covered in the mining gearbox spec map.
Trackable next signals: (1) confirm whether the EU Regulation 2023/1230 implementing acts in your product category have published the detailed conformity modules for transmission components, since that determines the documentation the supplier must ship with each gearbox; (2) watch the AGV and shuttle-density trend in warehouses, because higher start-stop frequency is pushing duty factors above the 1.5 baseline for rack-and-pinion stacker cranes that previously sat at 1.25.