A helical gear reducer is specified first by its shaft orientation (coaxial, parallel-shaft, or shaft-mounted hollow-shaft) and second by its torque class, with current product data showing output torque bands from 500 Nm up to over 10 kNm and input power from 0.06 kW to 4,000 kW [S1][S2][S3][S4][S5].
The global supply base is heavily concentrated in Chinese OEM/ODM manufacturers (Zhejiang, Anhui, Jiangsu provinces) and a smaller set of European engineering houses (Italy, Germany, Turkey); for any torque above 5 kNm the European catalogues list verifiable cataloged units, while for sub-1 kNm units Asian FOB-tier sourcing dominates [S6].
Topology and shaft orientation: coaxial vs parallel-shaft vs hollow-shaft
Coaxial helical reducers — input and output shafts on the same centerline — are the default for conveyor and mixer drives where a compact footprint and foot/flange mounting are required; Siti's NHL series exemplifies this, spanning 10 sizes with 3 input versions, ratios up to 466:1, max input power 210 kW and a max output torque of 12,000 Nm at speeds up to 3,000 rpm [S1]. For an in-depth baseline on coaxial design, see the helical gear reducer reference.
Parallel-shaft helical reducers — input and output shafts offset on parallel axes — handle higher radial loads and are preferred where belt or chain drives couple to the output; Galbiati's reversible hot-mill twin-drive unit delivers 4,000 kW at 80 rpm with a 960 mm roll center distance, illustrating the upper extreme of the parallel-shaft format [S2]. For background on parallel-shaft kinematics, refer to the industrial gear overview.
Hollow-shaft (shaft-mounted) helical reducers mount directly onto the driven machine's input shaft via a torque arm, eliminating coupling alignment; YILMAZ's DT series takes this to 350 rpm max, two- or three-stage ratios in a single housing, and accepts standard IEC B5 or B14 motor flanges plus an electromagnetic brake option [S3]. A related coupling reference for shaft-mounted output integration is the gear coupling page.
Torque, power, and ratio envelope
Torque class is the most useful first filter when matching a helical reducer to an application: Transtecno's CMG covers 500–1,000 Nm at 0.06–7.5 kW for light transmission duty [S4], FIMET's PE-A series occupies 2–5 kNm at 33 kW for shaft-mounted industrial duty [S5], while Siti's NHL and Galbiati's mill reducers both exceed 10 kNm at the heavy end of the catalog [S1][S2].
Ratio range drives gearbox size: NHL reaches 466:1 in a single cataloged family, while Chinese OEM modular series such as the FC line list 14 sizes from 07 to 167 with speed ratios from 1.3 to 289.74 and per-stage efficiencies near 98% after precision grinding [S1].
Below 1 kNm the Transtecno CMG modular line is built around configurable foot/flange/B14 input kits, showing how sub-1 kNm helical units are increasingly modularized like servo-class gear pump families [S4].
Speed envelopes are tightly tied to topology: coaxial units like the NHL reach 3,000 rpm input [S1]; hollow-shaft DT units cap at 350 rpm [S3]; mill-duty parallel-shaft reducers operate as low as 80 rpm at multi-megawatt power [S2]. Selecting outside these envelopes is a leading cause of premature bearing failure.
Mounting, flange standards, and material specification
Foot, flange, and shaft-mounted configurations are not interchangeable after the fact; specify the IEC flange code at order time. YILMAZ's DT series ships with IEC B14 and B5 input flanges as standard and uses GG20 and GGG40 cast-iron housings with case-hardened gears at 58–62 HRc [S3] — these hardness and housing grades are typical for the medium-and-heavy torque classes shown across the dataset [S3].
For shaft-mounted service, the hollow-shaft design carries higher overhung load capacity than an equivalent worm gearbox, which is why DT and similar lines are favored over worm reducers in conveyor and agitator duty where radial load on the output is significant [S3]. FIMET's PE-A series uses an aluminium housing coupled to compact-B5 or standard-B5 motors, trading cast-iron robustness for a 33 kW, 2–5 kNm lighter-duty package aimed at OEM skid builders [S5].
Modularity is a cost lever at sub-1 kNm: the FC series exposes 14 frame sizes and an explicit modular design intent, so plant engineers can swap input kits, output flanges, and ratios without changing the gearbox body — the same logic that governs a linear guide carriage family.
Selection criteria: matching duty, environment, and load profile
For continuous-duty conveyors, mixers, and agitators in the 0.5–5 kNm band, a shaft-mounted hollow-shaft helical unit is typically the lowest-total-cost option because it eliminates the coupling and baseplate. YILMAZ DT, FIMET PE-A, and the OEM FC series all target this duty cycle with torque ratings between 2 and over 10 kNm and 2- or 3-stage options [S3][S5].
For reversing or high-inertia mill drives (rolling mills, hoists, mixers with frequent direction changes), a parallel-shaft heavy-duty unit with documented reversing capability is required; the Galbiati reversible hot-mill twin-drive at 4,000 kW / 80 rpm is the documented benchmark in the current dataset, paired with a 960 mm roll center distance [S2]. For comparison, crossed roller guide duty cycles share the same reversing-load logic, even though the mechanism is different.
For light transmission and packaging machinery in the 500–1,000 Nm band, a coaxial modular unit such as the Transtecno CMG (0.06–7.5 kW) is the appropriate fit; specifying a heavy cast-iron unit in this band adds mass and cost without service-life benefit [S4].
Use cases, constraints, and failure modes
Documented application envelopes from the 2026-05 supplier refresh cover heavy-duty conveyors, hot mills, shaft-mounted industrial machinery, light transmission packaging lines, and OEM skid building [S1][S2][S3][S4][S5]. Outside these bands — for example, specifying a sub-1 kNm unit on a 1,500 kW mill drive, or a hollow-shaft unit in a cleanroom packaging line — operators should expect bearing or seal failure within the first design overhaul.
Key failure modes traceable to the cataloged design limits: overspeed (NHL input 3,000 rpm max [S1]), over-torque (PE-A 2–5 kNm ceiling [S5]), insufficient overhung load capacity on hollow-shaft units relative to belt or chain pull, and inadequate sealing for dusty or washdown environments — the NHL and DT lines both call out high-quality sealing as a design feature, indicating the cost of cheap seals [S1][S3].
On Alibaba, at least one Chinese supplier listed under helical gear reducers reports a 68.6% response rate, total revenue above US$100 million, and a domestic-market share of 60.0%; lead time and MOQ flexibility should still be qualified per order.
Sourcing, cost band, and verification checklist
Published FOB pricing for a general-purpose Chinese OEM helical gearbox sits in a 1.00–1,000.00 USD/set band with MOQ of 1 set and 5,000 sets/month supply capability for the cataloged supplier [S6]; another Zhejiang manufacturer lists 15,000 PCS/month capacity with negotiable MOQ.
Pre-shipment verification list: (1) confirm IEC flange code (B5 / B14) matches the driven motor; (2) confirm gear hardness (58–62 HRc is the current industry benchmark for case-hardened helical gearing [S3]); (3) confirm housing material (GG20 / GGG40 cast iron for heavy duty, aluminium for sub-5 kNm [S3][S5]); (4) confirm ratio, max input rpm, and max output torque against the driven machine's worst-case load, not nominal load. For cost context in adjacent power-transmission categories, see the planetary gearbox price and cost guide and the spherical roller bearing price 2026 for bearing-side cost drivers.
Trackable signals for the next procurement cycle: confirmation of the OEM FC series' availability across 14 frame sizes from Zhejiang and Anhui suppliers at the 1.00–1,000.00 USD FOB band; updated 2026-Q3 catalogs from Siti (NHL), YILMAZ (DT), and Galbiati (mill series) for any ratio extension or IEC flange addition; and any change in the documented 68.6% Alibaba response rate, which is the cleanest public proxy for supply-base health in this category [S6].