When a drive needs more muscle than the small SF frames can give, the SF87 helical worm gearbox steps in: 87 mm centre distance, robust 42CrMo shafts and a housing section designed for continuous shock loading. The unit follows the standard interface dimensions of the S87 frame family and is widely used on screw conveyors, industrial washers, kneaders and sawmill equipment.
Built for Heavy Duty
- Helical first stage takes motor speed down gently; worm stage delivers the final reduction
- Surface hardness HRC58~62 over a tough HRC33~40 core - hard skin, ductile heart
- Max temperature rise 40 °C (oil 50 °C), verified in factory run-in tests
- Choice of foot, flange or torque-arm mounting; solid or hollow output shaft
- Premium bearing brands (HRB, LYC, ZWZ, C&U or SKF/FAG/INA/NSK on request)
Technical Specification
| 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~ 68dB |
| Temp. rise (max) | 40°C |
| Temp. rise (oil) (max) | 5 0°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 |
Main fields of application:
- Chemical and environmental protection plants
- Building and construction machinery
- Wood, forest and recycling equipment
- Conveyors, mixers, agitators and hoists
- Textile, leather and paper industry
How to Order
Specify ratio, output speed, mounting position (M1-M6) and shaft direction; WGT returns a selection confirmation with efficiency, torque limits and a firm price. Sampling units for OEM validation are welcome. Production lead time is normally 5-10 weeks with sea or air freight from NINGBO / SHANGHAI. All SF87 gear reducers carry a one-year warranty and lifetime technical support.
Common Models in the SF Series
| Model | Centre distance | Output | Typical duty |
|---|
| 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 |
| SF77 | 77 mm | solid shaft, foot | turntables, elevators |
| 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 |
The table below lists the eight foot-mounted frames;
Naming makes selection easy: S = solid shaft, SA = hollow shaft, SAF = hollow shaft with flange, SAZ = torque-arm version - all sharing the same gear set and centre distance as the SF foot model.
Selection Example: Screw conveyor
Take a 7.5 kW, 1440 rpm motor driving a screw conveyor at 24 rpm. The ratio follows directly: 1440 / 24 = 60, ratio i=60. In this case the 87 mm frame accepts the shock loads of sticky material. The same three numbers - motor speed, target output speed, required torque - are all you need; our engineers (or the online selector below) cross-check the service factor for your duty cycle.
![how to size a gear reducer in 4 steps - gearbox selection flow]()
Application Cases
Wastewater treatment plant
A municipal wastewater plant replaced twelve ageing agitator drives with SA-series helical worm units. Sealed housings and NAK oil seals stood up to the humid atmosphere, and the hollow-shaft mounting let the maintenance crew swap units without touching the mixer shafts.
Textile dyeing lines
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.
Frequently Asked Questions
What warranty and documentation come with the gearbox?
A one-year warranty covers material and workmanship. Each unit ships with a test record (noise, temperature rise, backlash), dimension drawing and installation manual.
What is the difference between SF, S, SA, SAF and SAZ versions?
They share one gear set: SF is foot-mounted with solid shaft, S is shaft-mounted, SA has a hollow output shaft, SAF adds a flange, and SAZ is the torque-arm version. Pick by mounting, not by performance.
![industrial gearbox applications - conveyor mixer crusher wastewater]()
Get Your Drawing and Quotation within 24 Hours
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.
Or simply send your motor data (kW, speed, duty) and driven-machine details through the inquiry button - we reply with a completed datasheet, dimension drawing and factory price the same working day. Looking for a gear reducer for food processing machine? Tell us the duty point and we will confirm the model in writing.
