Description
GT7 GT Type Sleeve Coupling – 71–100mm Bore Rigid Muff Coupling for Zero-Backlash Shaft Connection
The GT7 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 190 mm outer diameter and 382 mm overall length, the GT7 provides a compact, maintenance-free rigid connection for 71–100 mm shaft diameters, rated at 6300 N·m nominal torque at up to 2800 rpm maximum speed. The GT7 at 6,300 N·m serves the 71–100 mm bore range of large industrial motors. At this torque level, the rigid sleeve coupling delivers the solid, zero-backlash connection needed for large pump, compressor, and mixer motor shaft connections without the complexity of flanged coupling alignment.
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 | GT7 |
| Type | GT Type Sleeve Coupling (Muff Coupling) |
| Bore Range (d) | 71–100 mm |
| Outer Diameter (D) | 190 mm |
| Overall Length (L) | 382 mm |
| Nominal Torque (Tn) | 6300 N·m |
| Maximum Speed [n] | 2800 rpm |
| Bore Tolerance | H7 standard |
| Keyway Standard | GB3852-1997 |
| Mass | 58.0 kg |
Dimension Reference
Construction and Functional Features
The GT7 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
- Industrial fan motor to shaft connections — centrifugal and axial fan rigid drive coupling
- Paper machine roll drive connections — sustained torque rigid shaft coupling
- Mining equipment auxiliary drives — conveyor and pump rigid shaft connections in hostile environments
- Marine auxiliary machinery drives — rigid coupling for auxiliary pump and fan motor shaft connections
For technical enquiries and volume supply information, visit our contact page.
Customer Reviews and Case Studies
★★★★★
United States — Industrial Mixer OEM
GT7 sleeve couplings connect motor shafts to gearbox inputs on our large industrial mixing equipment. At 6,300 N·m, the coupling covers our full mixer motor range and the 71–100 mm bore accommodates our standard motor shaft sizes.
— Applications Director, Chicago
★★★★★
Norway — Marine Equipment OEM
Specified for auxiliary machinery shaft connections on our offshore supply vessels. The GT7’s 2,800 rpm rating covers our auxiliary motor speeds and the all-steel rigid body meets our marine classification material requirements.
— Marine Engineer, Bergen
★★★★☆
Vietnam — Plastic Extrusion Equipment
Used on extruder gearbox input shaft connections. The GT7 sleeve coupling handles the sustained high torque of our plastic extrusion process and its rigid connection prevents the torsional play that would affect our product dimensional consistency.
— Production Engineer, Hanoi
Frequently Asked Questions
What drives the selection between GT7 and GT8 for a given application?
The primary selection driver is bore diameter: GT7 covers 71–100 mm; GT8 covers 90–125 mm. If your shaft diameter falls in the 90–100 mm overlap zone, GT7 is the lighter choice (58 kg vs 117 kg) and should be selected unless the application torque exceeds GT7’s 6,300 N·m rating, in which case GT8 (16,000 N·m) is required.
Can the GT7 sleeve coupling be used in an outdoor installation?
Yes. The cast steel body of the GT7 is suitable for outdoor installation. For permanent outdoor exposure, a protective coating (paint, galvanising, or epoxy) is recommended to prevent surface rust. The coupling should be covered by an appropriate guard to protect against weather ingress and debris.
What is the rotational speed limit basis for the GT sleeve coupling?
The speed limit is set by the peripheral velocity of the coupling OD — typically 30 m/s for cast iron and 50 m/s for cast steel, beyond which centrifugal stress becomes a design concern. The listed maximum speed [n] is the lower of the two limits (cast iron governs for smaller models). Always check the peripheral velocity at your operating speed against the allowable.
Is the GT sleeve coupling available in stainless steel?
The standard GT coupling is supplied in cast iron or cast steel. Stainless steel versions can be manufactured on request for corrosive environments (food processing, chemical, marine). Contact Ever Power with your material requirement when enquiring.
How should GT7 sleeve couplings be stored before installation?
Store in a dry, indoor environment away from direct sunlight and chemical exposure. Apply a light preservative oil to the bore and keyway surfaces to prevent rust during storage. Avoid stacking heavy items on top of the coupling to prevent bore deformation.
Source the GT7 GT Sleeve Coupling
Ever Power manufactures the GT7 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.