Buyers looking for a mid-size worm gear speed reducer with a helical pre-stage will find the SF47 a proven choice. The unit uses the same 47 mm centre distance family, and accepts all common IEC or NEMA motor flanges. Because the first stage is helical, the SF47 gearbox runs cooler and more efficiently than a single-stage worm unit at equal ratio.
Technical Data
Design Highlights
| 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 |
Design Highlights
- Helical + worm two-stage gearing: quiet input, high reduction in one compact block
- Gears in 20CrMnTi alloy steel, carburised to HRC58~62, core HRC33~40 for shock loads
- 42CrMo input/output shafts, tempered and finished to HRC25~30
- Lubricated for life under normal duty with Shell Omala or equivalent oil
- Vibration kept below 20 μm; backlash within 20 arcmin for stable positioning
Typical duty points where this unit is specified:
- Metal processing lines
- Building and construction machinery
- Agriculture and food processing
- Textile, leather and paper industry
- Wood, forest and recycling equipment
Ordering & Support
Every SF47 ships factory-tested: noise, temperature rise and backlash are recorded before packing in a standard wooden crate. Send us your ratio, output torque and mounting style - our engineers confirm the selection same day and quote EXW or CIF accordingly. Urgent units for emergency breakdowns can be air-freighted within 72 hours of payment.
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: Packaging line transfer
Take a 2.2 kW motor at 1420 rpm driving a transfer belt that needs 71 rpm. The ratio follows directly: 1420 / 71 = 20, so i=20 fits with margin. In this case the flanged SAF47 variant bolts directly to the belt drive shaft. 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
Flour mill screw conveyors
A flour mill standardised on SF57 gear reducers for its screw conveyor network. One spare-part pool now covers fifteen drives, and the smooth helical input stage keeps noise low in the packing hall.
Warehouse vertical lift
A logistics integrator selected SA67 units for pallet lifts. The hollow output bore carries the lift screw directly, and one year of three-shift operation has passed without a single seal replacement.
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.
![industrial gearbox applications - conveyor mixer crusher wastewater]()
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 gear reducer for screw conveyor? Tell us the duty point and we will confirm the model in writing.
