GB series flexible encoder coupling with anodised aluminium hubs and a figure-eight polyurethane element. It connects an encoder, tachometer or micro motor to a small lead screw or machine shaft, absorbing angular, parallel and axial misalignment so that no side load reaches the encoder bearings. Rated torque 1 N.m, outer diameters 15, 18 and 25 mm, bores 4 to 15 mm.
Technical specifications
| Series | GB |
|---|---|
| Coupling type | Flexible figure-eight (8-shape) elastomer coupling |
| Hub material | Aluminium alloy, anodised |
| Element material | Polyurethane |
| Rated torque | 1 N.m (manufacturer series rating) |
| Outer diameters | 15 mm, 18 mm, 25 mm |
| Bore range | 4 to 15 mm depending on outer diameter |
| Shaft attachment | Set screw (grub screw) on each hub |
| Hub orientation options | Convex (forward) hubs, concave (reverse) hubs, or one of each |
| Surface treatment | Anodised aluminium |
| Compliance | RoHS |
| Brand and origin | GND / Guangzhida, Dongguan, China |
| Typical applications | Encoders, tachometers, micro motors, small lead screws, light instrument drives |
Available sizes
Every size is ordered with two bore diameters, one for the driving shaft and one for the driven shaft. The hub orientation changes the overall length, so check the space you have between the two shaft ends before choosing.
| Size (outer diameter x length) | Bore range |
|---|---|
| 15 x 24 mm (concave / reverse hubs) | 4 to 8 mm |
| 15 x 31 mm (convex / forward hubs) | 4 to 8 mm |
| 15 x 28 mm (one convex + one concave) | 4 to 8 mm |
| 18 x 28 mm (concave / reverse hubs) | 4 to 10 mm |
| 18 x 38 mm (convex / forward hubs) | 4 to 10 mm |
| 18 x 32 mm (one convex + one concave) | 4 to 10 mm |
| 25 x 45 mm (concave / reverse hubs) | 6 to 15 mm |
| 25 x 55 mm (convex / forward hubs) | 6 to 15 mm |
| 25 x 50 mm (one convex + one concave) | 6 to 15 mm |
How to order
Couplings are quoted per order, with no price shown on the site. Send us the series GB, the outer diameter and length you need, and the two bore diameters, for example GB-18X38-8X10. If you do not know which size fits, send the motor shaft diameter, the driven shaft diameter, the torque and the space available between the two shafts, and our engineers select it for you. RendatSP ships to Saudi Arabia, Iraq, the UAE, Egypt, Oman, Libya, Morocco, Mauritania, Yemen, Algeria, Jordan and Syria.
Frequently asked questions
What is a figure-eight coupling and where is it used?
It is a flexible coupling in which two metal hubs grip a moulded polyurethane element shaped like a figure eight. The element carries the torque and flexes to take up misalignment. Torque capacity is low, so it is used on encoders, tachometers, micro motors and small lead screws rather than on power transmission drives.
How do I choose the bore combination?
Measure the two shafts. The first bore is for the motor or encoder shaft and the second for the driven shaft, and the two can be different, for example 8 mm on one side and 10 mm on the other. Send us both diameters and we supply the matching part.
Can I use it on a servo positioning axis?
Only on very light axes. Rated torque is 1 N.m and the elastomer element is flexible, so it introduces a small amount of wind-up. Where positioning accuracy matters, use a disc or bellows coupling instead, and we can quote the equivalent size.
Does it need a keyway?
No. Both hubs clamp on plain shafts with set screws, so no keyway is required. Make sure the set screw seats on a flat or on a clean shaft surface and tighten it to the torque marked on the hub.