The SF77 gear reducer extends the helical-worm concept into medium torque territory. Its 77 mm centre distance and generously sized output shaft make it a straightforward match for existing S77 installations on mixers, turntables and heavy conveyors. For machine builders the attraction is simple: one compact speed reducer that handles ratios a single worm stage could only reach with much higher losses.
Engineering Notes
- Two-stage helical + worm layout; overall efficiency 94%~96% depending on ratio
- Cast-iron housing HBS190-240 resists impact loads and harsh site conditions
- Gears in case-hardened 20CrMnTi, ground to grade 6~5; noise stays between 60 and 68 dB
- Backlash ≤20 arcmin and vibration ≤20 μm keep the drive smooth under reversing loads
- Heat treatment: tempering, carburising and quenching on the critical gear faces
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 |
Where customers install this series:
- Metal processing lines
- Building and construction machinery
- Textile, leather and paper industry
- Wood, forest and recycling equipment
- Conveyors, mixers, agitators and hoists
Packing & After-Sales
Units are rust-protected, boxed with an installation manual and packed in export-grade wooden crates for NINGBO or SHANGHAI shipment. WGT supports every SF77 gearbox with a one-year warranty, spare seal and bearing kits, and engineering advice on oil change intervals. Send your specification - drawings, torque curves and a firm quotation come back within 24 hours.
Selection Example: Rotary turntable
Take a 5.5 kW motor at 960 rpm rotating a turntable at 12 rpm. The ratio follows directly: 960 / 12 = 80, i=80 within one unit. In this case backlash below 20 arcmin keeps the indexing position repeatable. 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]()
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.
Application Cases
Rotary indexing table
A machine builder drives a two-metre indexing table with an SF77 reducer. Backlash within 20 arcmin keeps positioning repeatable, which mattered more to the customer than the price difference to a plain worm unit.
Sawmill crushing line
A wood-processing plant drives its crusher with an SF97 unit. The cast-iron housing (HBS190-240) resists impact, and the high-torque worm stage starts the crusher under load without a soft-starter.
![industrial gearbox applications - conveyor mixer crusher wastewater]()
Frequently Asked Questions
Can this unit mount on my existing installation without redesign?
Yes - the series is manufactured to the same centre distances, shafts and flange dimensions of the common industry frames, so couplings, guards and foundations stay untouched.
How do I calculate the ratio I need?
Divide motor speed by the target output speed (i = n1/n2), then check the required torque against the rating table with your service factor. The online selector below does this automatically.
Get Your Drawing and Quotation within 24 Hours
One minute, one model. Skip the back-and-forth: configure your drive in the WGT Motor & Gearbox Online Selection System and send us the result for a same-day quotation.
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 gearbox for wastewater treatment? Tell us the duty point and we will confirm the model in writing.
