Description
STS7-25 Stainless Steel Setscrew Rigid Coupling – 25 mm OD 316SS Mid-Range Precision Shaft Connector
The STS7-25 is the 316 stainless steel equivalent of the TS7-25 aluminum alloy model, offering the same 25 mm outer diameter, 38 mm length, bore range of 8 to 12 mm, and 1 N·m nominal torque rating in a corrosion-resistant material body. The M4 setscrew thread and 1.7 N·m tightening torque are retained from the aluminum version. Where the TS7-25 is the standard choice for indoor, low-humidity precision automation, the STS7-25 is specified when the application environment introduces chloride, solvent, steam, or salt-spray exposure that would degrade an aluminum alloy body over time.
The mass of the STS7-25 is 100 g — approximately 2.6 times that of the 39 g TS7-25 — and the moment of inertia increases to 7.1 × 10⁻⁶ kg·m². For standard servo axis designs in the 200–500 W motor range, this inertia contribution remains well within typical servo amplifier stability margins. The STS7-25 is used across food packaging OEM machines, pharmaceutical process equipment, chemical industry automation, and marine instrument drives — wherever the 8–12 mm bore range and 1 N·m torque class are required in a corrosion-resistant coupling.
For a complete side-by-side comparison of the TS7-25 and STS7-25 with all other series models, visit our product catalog.
Technical Specifications
| Parameter | Value |
|---|---|
| Model | STS7-25 |
| Body Material | 316 Stainless Steel |
| Outer Diameter (D) | 25 mm |
| Overall Length (L) | 38 mm |
| Hub Length (L1) | 9 mm |
| Available Bore Sizes | 8, 10, 11, 12 mm |
| Setscrew Thread | M4 |
| Wrench Torque | 1.7 N·m |
| Rated Torque | 1 N·m |
| Maximum Torque | 2 N·m |
| Maximum Rotational Speed | 14,000 rpm |
| Moment of Inertia | 7.1 × 10⁻⁶ kg·m² |
| Mass | 100 g |
Dimension Drawing
316 Stainless Steel — Material Advantages in the STS7-25 Context
At the 25 mm OD, 8–12 mm bore, and 1 N·m torque class, the STS7-25 serves a broad cross-section of industrial automation applications. The choice between aluminum TS7-25 and stainless STS7-25 is a material environment decision. Food processing lines with daily washdown using caustic soda or sodium hypochlorite solutions will corrode aluminum alloy over time — often within weeks in aggressive CIP environments. Pharmaceutical production in ISO-classified rooms may mandate stainless for material audit purposes even without active chemical exposure. Marine and coastal installations benefit from the molybdenum-enhanced chloride resistance of 316SS regardless of direct splash exposure. In all these cases, the STS7-25 delivers the same zero-backlash, high-speed, rigid transmission performance as its aluminum counterpart while lasting significantly longer in the operating environment.
Typical Applications
- Food packaging encoder connections — stainless servo drives on shrink-wrap, tray-seal, and vacuum pack machines
- Pharmaceutical tablet coating pan tilt encoder — solvent atmosphere environment
- Chemical reactor instrumentation drives — corrosive vapour zone position feedback
- Offshore instrument positioning — corrosion-critical environments on vessels and platforms
- Brewery and dairy process drives — CIP-cleaned production zones
Customer Reviews and Case Studies
★★★★★
Belgium — Food Packaging OEM
We specify the STS7-25 across our vacuum packaging machines for fresh produce. The encoder connections are in a zone washed with chlorinated water after every shift. Aluminum couplings corroded within 3 months. The stainless versions have been maintenance-free for 26 months.
— Senior Engineer, Ghent
★★★★★
United States — Pharmaceutical Equipment
Used on tablet coating pan tilt drives in an acetone and ethanol solvent atmosphere. 316SS was the only acceptable material for this zone. The STS7-25 met our material specification and dimensional accuracy was confirmed on incoming inspection.
— Validation Engineer, New Jersey
★★★★☆
Saudi Arabia — Petrochemical Plant Maintenance
Replacement couplings for process valve position feedback in an H2S environment. The 316SS body has shown no corrosion in 14 months. The 10/12 mm bore matched our existing shafts without any modification.
— Maintenance Engineer, Jubail
Frequently Asked Questions
What is the bore range of the STS7-25?
8, 10, 11, and 12 mm on each side independently. Any combination within this range can be specified at standard pricing.
Is the STS7-25 compatible with organic solvent atmospheres?
Yes. 316 stainless steel resists most common organic solvents — alcohols, ketones, esters — at ambient temperature. For concentrated strong acids at elevated temperatures, verify chemical compatibility with a material resistance guide.
What wrench torque is specified for the STS7-25 setscrews?
1.7 N·m for the M4 setscrews. Use a calibrated hex key or torque driver. This applies to both the TS7-25 aluminum and STS7-25 stainless versions.
Can the STS7-25 withstand steam cleaning?
316 stainless steel withstands steam cleaning at temperatures up to approximately 150°C without dimensional change or corrosion. This covers standard food and pharmaceutical steam-clean protocols.
Are dimensional drawings available for the STS7-25?
Yes. PDF and DXF drawings are available on request. Contact Ever Power with your model number and bore configuration for rigid coupling drawing provision.
Enquire About the STS7-25 Stainless Rigid Coupling
Ever Power supplies the STS7-25 and the full STS7 stainless series direct from our manufacturing facility. Provide bore requirements, quantity, and application details for a factory-direct response.
