The SA77 hollow shaft worm gear unit sits in the middle of the SA range, where torque is high enough that a coupling becomes a maintenance item in its own right. Mounting the unit directly on the driven shaft removes that item: no keys to shear, no elastomer elements to age, no re-alignment after the first year. A helical pre-stage keeps efficiency at 94~96% while the worm stage delivers the final ratio and the self-locking tendency.
Mid Range Torque, Zero Coupling
- Hollow output from 30 mm bore upward, keyed or shrink disc, machined in one setup with the housing
- Torque arm and reaction rod in a choice of positions, so the unit can sit wherever the machine allows
- 42CrMo shafts, quenched and tempered to HRC25~30, for the reversing loads shaft mounting creates
- Backlash 20 arcmin or less and vibration 20 μm or less, which keeps the driven shaft steady
- Lifetime lubrication on normal duty with GB L-CKC220~460 / Shell Omala 220~460
SA77 Data Sheet
| Housing material | Cast iron/Ductile iron |
| Housing hardness | HBS190-240 |
| Gear material | 20CrMnTi alloy steel |
| Surface hardness of gears | HRC58~62 |
| Gear core hardness | HRC33~40 |
| Input / Output shaft material | 42CrMo alloy steel |
| Input / Output shaft hardness | HRC25~30 |
| Machining precision of gears | precision grinding, grade 6~5 (ISO 1328) |
| Lubricating oil | GB L-CKC220~460 / Shell Omala 220~460 |
| Heat treatment | tempering, cementit-ing, quenching, etc. |
| Efficiency | 94%~96% (depends on the transmission stage) |
| Noise (max) | 60~68 dB |
| Temp. rise (max) | 40 C |
| Temp. rise (oil) (max) | 50 C |
| Vibration | ≤20μm |
| Backlash | ≤20Arcmin |
| Brand of bearings | HRB/LYC/ZWZ/C&U (SKF, FAG, INA, NSK optional) |
| Brand of oil seal | NAK -- Taiwan or other brands requested |
Proven in service across these industries:
- Conveyors, mixers, agitators and hoists
- Building and construction machinery
- Mining and bulk material handling
- Agriculture and food processing
- Wastewater treatment and water supply
Ordering and Support
Send us the machine shaft diameter, the required ratio and the mounting space and we return a drawing set that shows the reaction points, the clamping method and the oil-level marks for your mounting position. Units ship from NINGBO or SHANGHAI in export crates, factory-tested, with a one-year warranty and seal and bearing kits held in stock.
Field Applications
Automatic car-wash line
A car-wash equipment builder fits SA57 hollow-shaft reducers to its conveyor chains. The compact frame hides inside the wash tunnel, and FKM seal options handle the constant moisture.
Textile dyeing drums
A dyeing machine maker uses SF67 speed reducers on its fabric-turning drums. Low vibration (under 20 microns) prevents streaks in the fabric, and the 94-96% efficiency keeps the heat load down in a warm workshop.
![where gear reducers are used in industry]()
Where these units are installed across industry.
Selection Example: Screw feeder on a silo outlet
Take a 5.5 kW motor at 960 rpm turning a screw feeder at 16 rpm. The ratio follows directly: 960 / 16 = 60, so i=60 is chosen. In this case shaft mounting keeps the drive off the floor and clear of the discharge chute. Once the ratio is fixed, check the required output torque against the rating table with the service factor applied - that is what decides the frame, not the ratio alone.
![gearbox selection guide: speed, torque, service factor]()
How a ratio and a frame size are determined, step by step.
Frame Sizes and Typical Duties
| Model | Centre distance | Output | Typical duty |
|---|
| SF77 | 77 mm | solid shaft, foot | turntables, elevators |
| SF37 | 37 mm | solid shaft, foot | small conveyors, dosing |
| SF47 | 47 mm | solid shaft, foot | packaging, dosing pumps |
| SF57 | 57 mm | solid shaft, foot | belt conveyors, stirrers |
| SF67 | 67 mm | solid shaft, foot | mixers, feeders |
| SF87 | 87 mm | solid shaft, foot | screw conveyors, washers |
| SF97 | 97 mm | solid shaft, foot | thickeners, kilns |
| SF107 | 107 mm | solid shaft, foot | heavy material handling |
Read the frame number as the centre distance in millimetres. Shaft and mounting styles are separate choices: solid shaft (S), hollow shaft (SA), flanged hollow shaft (SAF) and torque arm (SAZ).
From Duty Point to Delivery in One Working Day
Stop guessing the ratio. Engineers can size the unit themselves in the WGT Motor & Gearbox Online Selection System - input speed, torque and duty, get the model instantly.
Tell us what the machine does and how hard it works; we calculate the ratio, apply the service factor and send back the drawing and quotation within one working day, including sea-freight and air-freight options. Looking for a gearbox for mixer and agitator? Tell us the duty point and we will confirm the model in writing.
Common Questions from Buyers
How do I choose between a helical-worm and a helical-bevel gearbox?
For a right-angle drive at a moderate ratio and the lowest cost per unit, a helical-worm unit is normally the better buy. When the ratio is low and efficiency is the priority, a helical-bevel (K series) unit wins - it holds 96% and above at any ratio, while the worm stage loses a little efficiency as the ratio grows.
What mounting positions (M1 to M6) are available?
The S series supports M1 to M6 mounting positions, so the unit can be installed on its base, wall or ceiling. The oil level plug is repositioned accordingly; state the position when ordering so the unit is filled and labelled correctly.
Can the reducer be supplied with a brake motor or an IEC motor flange?
Yes. We supply the reducer as a bare unit with an IEC standard input flange, and you can bolt on any IEC or NEMA motor - including a brake motor. The flange dimensions follow the common IEC pattern, so existing motors drop straight on.
