Description
GT8 GT Type Sleeve Coupling – 90–125mm Bore Rigid Muff Coupling for Zero-Backlash Shaft Connection
The GT8 GT type sleeve coupling — also known as a muff coupling — is the simplest and most direct form of rigid shaft coupling: a single cylindrical steel body with a through bore machined to receive two co-linear shaft ends, transmitting torque through keyway and fitted key engagement on each shaft side. At 240 mm outer diameter and 482 mm overall length, the GT8 provides a compact, maintenance-free rigid connection for 90–125 mm shaft diameters, rated at 16000 N·m nominal torque at up to 2240 rpm maximum speed. At 16,000 N·m and 90–125 mm bore, the GT8 serves the largest directly coupled industrial drive applications. The one-piece steel body at 117 kg provides a structurally robust rigid connection for large pump, fan, and gearbox input shaft connections in the 500 kW–1 MW power range.
The operating principle of the GT sleeve coupling is direct and reliable. Each shaft end is inserted into one half of the sleeve bore. A fitted key is placed in the matching keyways of both the shaft and the sleeve bore on each side — two keys total, typically positioned 180° apart. When the coupling rotates, torque is transmitted from the driving shaft to the sleeve through key-keyway bearing contact, and from the sleeve to the driven shaft through the same mechanism on the opposite side. There are no flexible elements, no preloaded fasteners to maintain, and no wear surfaces subject to degradation under normal operating conditions. The result is a permanent, zero-backlash connection that requires essentially no maintenance throughout its service life, provided the connected shafts remain accurately aligned.
The H7 bore tolerance and GB3852-1997 keyway standard ensure dimensional compatibility with standard motor and driven equipment shaft ends throughout the GT series. For special shaft configurations — non-standard diameters, tapered bores, or hydraulic fit bores — custom machining is available. The complete GT series, from GT1 through GT10, is listed on our product catalog page.
Technical Specifications
| Parameter | Value |
|---|---|
| Model | GT8 |
| Type | GT Type Sleeve Coupling (Muff Coupling) |
| Bore Range (d) | 90–125 mm |
| Outer Diameter (D) | 240 mm |
| Overall Length (L) | 482 mm |
| Nominal Torque (Tn) | 16000 N·m |
| Maximum Speed [n] | 2240 rpm |
| Bore Tolerance | H7 standard |
| Keyway Standard | GB3852-1997 |
| Mass | 117 kg |
Dimension Reference
Construction and Functional Features
The GT8 body is machined from high-quality cast iron or cast steel — material selection dependent on model size and rated torque. The bore is machined to H7 tolerance to provide a controlled fit against the shaft end, complementing the key-keyway torque transmission with a stable radial contact between shaft and bore. The outer diameter is machined concentric with the bore to ensure rotational balance. Keyway slots are machined to GB3852-1997 standard dimensions for the specified bore size — verifying compatibility with standard motor shaft keyways without modification.
Zero Backlash
Rigid key-keyway torque transmission with no play or compliance — every angular increment on the driving shaft is replicated exactly on the driven shaft. Essential for phase-critical and encoder feedback applications.
Maintenance-Free Service Life
No wear elements, no elastomeric components to degrade, no bolts to retorque. Once correctly installed on aligned shafts, the GT sleeve coupling requires no maintenance throughout its service life.
Compact One-Piece Design
Single cylindrical body — no bolted flanges, no split halves, no external fasteners. Lowest-profile rigid coupling available for co-linear shaft connections, minimising guard size and axial space requirements.
Standard Keyway Compatibility
Bore and keyway dimensions to GB3852-1997 and H7 bore tolerance ensure direct compatibility with standard motor and driven equipment shaft ends throughout the industrial motor range.
Manufacturing Quality
Typical Applications
- Large centrifugal pump motor connections — high-torque direct drive rigid coupling
- Power station auxiliary equipment drives — boiler feed pump and fan motor shaft connections
- Primary industrial conveyor drives — heavy-duty rigid shaft coupling for main belt conveyor drives
- Ball mill and crusher auxiliary drives — large industrial drive rigid shaft coupling
For technical enquiries and volume supply information, visit our contact page.
Customer Reviews and Case Studies
★★★★★
Germany — Large Industrial Pump OEM
GT8 sleeve couplings connect 90–125 mm motor shafts to pump impeller shafts on our largest centrifugal pump range. The 16,000 N·m torque rating covers all pump models in our range and the one-piece steel body eliminates the alignment sensitivity of bolted flange connections at this torque level.
— Chief Engineer, Hamburg
★★★★★
Malaysia — Petrochemical Plant
Installed on product transfer pump drive shaft connections. The GT8 handles our operating torque reliably and the rigid connection has maintained shaft concentricity within our 0.02 mm acceptance limit across 18 months of continuous operation.
— Plant Engineer, Kuala Lumpur
★★★★☆
Chile — Mining Processing Plant
Used on concentrate pump drive connections. The GT8 sleeve coupling accommodates our 100 mm pump shaft and 110 mm motor shaft with the appropriate bore combination, and has operated without maintenance through our continuous mining production schedule.
— Maintenance Superintendent, Antofagasta
Frequently Asked Questions
What is the key length engaged in each shaft end of a GT8 sleeve coupling?
The total sleeve length L covers both shaft insertions. For a standard symmetrical installation, each shaft end is inserted approximately L/2 into the sleeve. The key engagement length per shaft end is slightly less than L/2, accounting for the central clearance between shaft ends. The key length is typically 0.9–1.0× the shaft insertion depth.
Can the GT8 be used for a pump-motor set mounted on separate baseplates?
Yes, but careful alignment is critical. The rigid sleeve coupling transmits any residual misalignment as bending stress to the shaft bearings. For separate-baseplate installations where thermal growth or settlement may cause misalignment over time, a flexible coupling with misalignment compensation may be more appropriate. If GT8 is specified, use a laser alignment tool and recheck alignment after thermal stabilisation.
What is the mass of the GT8 sleeve coupling and how does it affect inertia?
The GT8 weighs 117 kg. The rotational inertia of the sleeve should be calculated and added to the driven machine inertia for motor sizing and soft-start calculations. A solid cylinder approximation gives J ≈ (m × r²)/2 where r is the OD radius — for GT8: J ≈ (117 × 0.12²)/2 ≈ 0.84 kg·m².
Is keyway-free (interference-only) torque transmission possible with GT8?
For light-duty applications within the interference fit friction capacity, keyway-free connections are occasionally used. However, for the GT8’s rated torque of 16,000 N·m, keyway engagement is required to achieve reliable torque transmission. Interference-only connections at this torque level would require impractically tight fits or large contact lengths.
What installation tools are needed for the GT8 sleeve coupling?
Due to its 117 kg mass and large bore, GT8 installation requires a lifting device (crane or hoist), a hydraulic press or heating arrangement for interference-fit installation, a calibrated torque wrench for any set screws, and a dial indicator for post-installation concentricity check. Heating the sleeve to 80–120°C before installation onto an interference-fit shaft is the recommended assembly method.
Source the GT8 GT Sleeve Coupling
Ever Power manufactures the GT8 and the complete GT sleeve coupling series — GT1 through GT10, covering 12 mm to 200 mm bore — direct from our factory. Specify bore diameters, keyway requirements, and any non-standard dimensions for a prompt technical and commercial response.