Description
STS7-40 Stainless Steel Setscrew Rigid Coupling – 40 mm OD 316SS Heavy-Duty Corrosion-Resistant Coupler
The STS7-40 is the largest and highest-torque model in the STS7 stainless steel series, delivering 5 N·m rated torque at up to 8,000 rpm through a 40 mm outer diameter 316 stainless steel body. With bore options from 14 to 20 mm, it serves large-frame servo motor and gearhead output connections in environments where the highest level of corrosion resistance in the TS7/STS7 family is required. The M5 setscrew thread and 1.7 N·m wrench torque are the same as the TS7-40 aluminum equivalent. All torque, speed, and geometric specifications are identical between the two material variants.
The STS7-40 weighs 210 g — 2.1 times the 100 g TS7-40 — and the moment of inertia is 2.4 × 10⁻⁶ kg·m². For servo axis inertia calculations in the motor power range this coupling serves (typically 750 W to 2 kW), the additional coupling inertia remains small relative to load-side inertia and within normal servo stability limits. For very high-acceleration, low-load applications, include this figure in the servo amplifier inertia ratio check.
Material traceability certificates are available with every order on request — a standard requirement for offshore, food safety, and pharmaceutical procurement. The full STS7 stainless coupling range is detailed on our product catalog page.
Technical Specifications
| Parameter | Value |
|---|---|
| Model | STS7-40 |
| Body Material | 316 Stainless Steel |
| Outer Diameter (D) | 40 mm |
| Overall Length (L) | 50 mm |
| Hub Length (L1) | 12 mm |
| Available Bore Sizes | 14, 16, 18, 19, 20 mm |
| Setscrew Thread | M5 |
| Wrench Torque | 1.7 N·m |
| Rated Torque | 5 N·m |
| Maximum Torque | 10 N·m |
| Maximum Rotational Speed | 8,000 rpm |
| Moment of Inertia | 2.4 × 10⁻⁶ kg·m² |
| Mass | 210 g |
Dimension Drawing
Why the STS7-40 in Demanding Environments
The STS7-40 occupies the intersection of high torque capacity and maximum corrosion resistance within the TS7/STS7 product family. At 5 N·m rated torque, it serves drive axes that are beyond the capacity of smaller precision couplings; the 316 stainless body extends this performance into environments — meat processing, fish handling, chemical reactors, offshore platforms, desalination plants — where the daily operating environment would degrade an aluminum coupling within weeks. The STS7-40 is not simply a corrosion-resistant upgrade: it is the correct engineering choice for applications that combine high torque demand with environmental aggression. A shaft flat on both shaft ends is recommended at this frame size for all torque levels near or above the rated 5 N·m.
Typical Applications
- Large servo encoder connections on stainless washdown conveyors in meat and fish processing plants
- Chemical reactor agitator position feedback drives in solvent and acid atmosphere zones
- Offshore platform instrument and valve actuator drives in salt-spray, high-humidity environments
- Pharmaceutical lyophiliser door drive encoder connections in CIP-qualified environments
- Desalination plant actuator feedback shafts with continuous brine-spray exposure
Customer Reviews and Case Studies
★★★★★
United Kingdom — Meat Processing Equipment
We manufacture stainless washdown conveyor systems for beef processing plants and the STS7-40 is our standard servo encoder coupling for the largest drive axes. The 20 mm bore matches our motor output shaft, and the 316SS body survives daily chlorine washdown without a mark. In use for over two years.
— Design Engineer, Leeds
★★★★★
Spain — Chemical Process Plant
Installed on servo-driven chemical dosing pump encoder connections in a concentrated HNO3 vapour zone. 316SS was the only material acceptable to our process safety team. Performing correctly for 16 months with no corrosion or mechanical issues.
— Process Engineer, Tarragona
★★★★☆
UAE — Desalination Plant Operator
Replacement couplings for valve actuator position encoders in our brine pump hall — one of the harshest salt-corrosion environments possible. The STS7-40 has maintained its condition over 12 months where stainless was the absolute minimum material requirement.
— Instrumentation Engineer, Abu Dhabi
Frequently Asked Questions
What is the maximum bore size for the STS7-40?
20 mm. Available bores are 14, 16, 18, 19, and 20 mm, selectable independently for d1 and d2.
How does the STS7-40 mass compare to the TS7-40?
The STS7-40 weighs 210 g versus 100 g for the aluminum TS7-40 — a 2.1× mass increase due to the density difference between 316 stainless steel and aluminum alloy.
Is a shaft flat necessary at 5 N·m with the STS7-40?
A machined shaft flat is strongly recommended for all bore sizes when operating at or near rated torque. At 20 mm bore with an M5 setscrew, the flat substantially improves grip and prevents shaft rotation within the bore under high torque.
Does 316SS maintain its properties at elevated temperatures?
316 stainless steel retains its mechanical properties and corrosion resistance up to approximately 300°C in continuous service — well above any likely coupling operating temperature in industrial applications.
Can material traceability documentation be supplied with the STS7-40?
Yes. Material mill certificates with heat number traceability and chemical composition analysis are available on request. Standard for offshore, petrochemical, and regulated industry procurement.
Request Pricing for the STS7-40 Stainless Rigid Coupling
Ever Power manufactures the STS7-40 and the complete STS7 stainless series in-house, with 316SS material traceability certificates available on request. Submit bore requirements, quantity, and application details.
