Flexible Shaft Couplings

Jaw Couplings

Plum blossom jaw couplings for industrial power transmission — vibration damping, misalignment compensation, and zero lubrication across a wide torque range.

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What Is a Jaw Coupling?

A plum blossom jaw coupling — also called a spider coupling or claw coupling — is a three-piece flexible shaft coupling that transmits torque through an elastomeric spider element compressed between two interlocking hub claws. The polyurethane spider absorbs shock, damps vibration, and compensates for angular, radial, and axial shaft misalignment, all without requiring grease or scheduled lubrication.

GBC supplies the complete GB/T5272-2002 plum blossom coupling family — from general-purpose drives to integrated brake-wheel and disc-brake variants — covering torque from 16 N·m to 25,000 N·m with bore sizes up to 160 mm. Browse the full range below or contact our engineering team for selection assistance.

16–25k

Torque range (N·m)

-35°~+80°C

Spider operating range

3 grades

Polyurethane hardness options

<15 min

Typical in-situ spider swap

🔄

Zero Lubrication Polyurethane spider — maintenance-free in service

🔥

Vibration Damping Three hardness grades for any shock load profile

⚙

In-Situ Spider Swap Replace elastomeric element without moving the machine

📈

Wide Torque Range 16 N·m to 25,000 N·m across the full family

⚡

Electrically Isolating Non-conductive spider prevents galvanic coupling

Product Range

Plum Blossom Jaw Coupling Types

Standard

LM / ML Type — Basic Jaw Coupling

Torque: 16–8,000 N·m (13 sizes)
Bore: up to 160 mm
Speed: up to 15,300 rpm
Spider: in-situ replacement, axial slide

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Double Flange

LMS / MLS Type — Double-Flange Jaw Coupling

Torque: 25–25,000 N·m (13 sizes)
Spider: radial removal, no shaft movement
For fixed-shaft and heavy-plant drives
Ideal where realignment must be avoided

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LMZ-I type jaw coupling with split brake wheel

Brake — Split Drum

LMZ-I Type — Split Brake Wheel Coupling

Torque: 250–25,000 N·m (15 configs)
Brake drum: Dia. 160–800 mm
Split drum replaceable radially in situ
Hoist, crane and winder drives

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LMZ-II type jaw coupling with integral brake wheel

Brake — Integral

LMZ-II Type — Integral Brake Wheel Coupling

Torque: 250–12,500 N·m (15 configs)
Brake drum: Dia. 160–800 mm
Most compact L0 in the brake range
Elevator and space-constrained drives

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Brake — Disc

MLP Type — Brake Disc Coupling

Torque: 630–12,500 N·m (9 sizes)
Disc: Dia. 355–1,000 mm
Caliper disc brake — superior heat control
VFD drives, precision hoists, automation

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Engineering Guidance

How to Select a Jaw Coupling

Step 1 — Calculate Design Torque

Apply the service factor K to account for shock, cyclic loads, and drive type before selecting a size. Never select on nameplate motor torque alone.

T_C = K x 9,550 x P / N ≤ T_n

K = service factor | P = motor power (kW) | N = speed (rpm) | T_n = nominal torque of selected size

Step 2 — Service Factor Reference

Load Character	K
Smooth / uniform (centrifugal pump, fan)	1.25–1.50
Moderate shock / cyclic (compressor, mixer)	1.50–2.00
IC engine, moderate shock	2.00–2.50
Heavy shock / frequent reversal	2.50–3.00

Step 3 — Choose the Right Type

Requirement	Recommended Type
General drive, easy axial access	LM / ML
Fixed shafts, no axial movement	LMS / MLS
Drum brake, frequent wheel wear	LMZ-I
Drum brake, compact space	LMZ-II
Disc brake, VFD or precision drive	MLP

Step 4 — Shaft Hole Types

Code	Description	Common Use
Y	Long cylindrical bore	Motors, gearboxes
J / J1	Short bore (J with counterbore)	Space-constrained
Z	Tapered 1:10 bore	Precision / zero-backlash

Unsure which type suits your application? Send us your motor power, speed, and shaft diameters and we will recommend the correct size and type within 24 hours.

Elastomeric Insert

Polyurethane Spider Hardness Grades

The spider is the only wear element in a jaw coupling and the one variable that most affects performance. All three grades operate across -35 °C to +80 °C and require no lubrication. Select based on torque capacity and vibration-damping priority.

shA

Shore 80 +/- 5

General Purpose

The default choice for most industrial drives. Balances torque capacity and vibration damping for centrifugal pumps, fans, compressors, and general machinery.

Torque capacity

Vibration damping

shB

Shore 92 +/- 5

High Torque

Raises torque capacity approximately 40–60% versus shA with slightly less damping. Specified for heavy-duty drives where shock loads are modest and maximum torque throughput is required.

Torque capacity

Vibration damping

shD

Shore 60 +/- 5

Maximum Damping

Softest grade — maximises vibration and shock absorption for sensitive drives, printing machinery, textile equipment, and VFD-driven applications where resonance must be controlled.

Torque capacity

Vibration damping

Industries Served

Jaw Coupling Applications

🔄 Water & Wastewater

Centrifugal and submersible pump drives. No grease — no contamination risk in treatment plant environments.

🏠 HVAC & Fans

High-speed fan and air-handling drives up to 15,300 rpm. shD spider controls resonance on VFD-driven units.

📦 Conveyor & Packaging

Start-stop conveyor and form-fill-seal drives. Compact axial footprint suits gearbox-motor arrangements.

⛏ Mining & Mineral Processing

Slurry pump and belt drive couplings in ductile iron. Robust under impact and water ingress.

🏭 Hoists & Cranes

LMZ-I and LMZ-II integrate drum brakes directly. Brake wheel serviceable without disturbing drive alignment.

🏭 Steel & Metals

Rolling mill auxiliaries and continuous caster drives where axial hub movement is impractical.

💉 Pharmaceutical

Mixer and coating drum drives. Electrically isolating spider, no grease — suitable for GMP environments.

🏫 Automated Warehousing

AS/RS stacker crane drives with MLP disc brake. Consistent stopping accuracy over millions of cycles.

Common Questions

Jaw Coupling FAQ

What is a plum blossom jaw coupling?

A plum blossom jaw coupling is a three-piece flexible shaft coupling comprising two hubs with interlocking claw faces and a six-lobed polyurethane spider element between them. The spider transmits torque while absorbing shock, damping vibration, and compensating for shaft misalignment. The name "plum blossom" refers to the flower-like shape of the spider element.

How often does the spider need to be replaced?

Under normal operating conditions, inspect the spider every 6–12 months. Replace immediately on visible cracking, permanent set, hardness loss, or when the drive develops unusual vibration. In high-shock duty (service factor K above 2.5), inspect every 3–4 months. Replacement takes under 15 minutes for most sizes and requires no special tools.

What shaft misalignment can a jaw coupling tolerate?

Standard LM/ML type: angular misalignment up to 2 degrees, radial offset 0.5–1.8 mm depending on size, and axial float 1.2–5.0 mm depending on size. These limits are for continuous operation; brief excursions beyond these values during installation or thermal expansion are tolerated but should not be continuous. Always align shafts as accurately as possible at installation — the coupling's compensation capacity is a tolerance allowance, not a substitute for alignment.

Can jaw couplings be used with variable frequency drives?

Yes, and they are commonly specified on VFD-driven machines. The shD (Shore 60) spider is recommended for VFD applications because its softer compound provides better absorption of the torque ripple and speed-reversal transients generated during ramp-up, ramp-down, and speed changes. The MLP brake-disc variant is the preferred choice when precise braking control is also required.

What is the difference between LMZ-I and LMZ-II?

LMZ-I has a split brake wheel in two bolted halves that can be removed radially without any shaft or hub movement — the drum is replaceable in situ. LMZ-II has the brake drum cast integrally into the hub body, giving the most compact total length (L0) in the family but requiring hub removal to replace a worn drum. Choose LMZ-I when brake wear is frequent; choose LMZ-II when axial space is the binding constraint and brake drum replacement is infrequent.

When should I choose LMS over LM?

Choose LMS when both shaft ends are rigidly supported and axial hub movement would require realignment of precision machinery — for example, a gearbox output directly coupled to a pump with close-coupled bearing housings, or multi-stage pump sets where moving either shaft risks disturbing the mechanical seal. The LMS double-flange design allows the spider to be replaced radially without any shaft movement.

Are spider elements interchangeable between LM sizes?

Spider elements (MT1–MT14) are size-specific — each coupling size uses one designated spider type. Spiders are not interchangeable between sizes, though the same spider element is available in all three hardness grades (shA, shB, shD) for every size. Always specify the coupling size and hardness grade when ordering replacement spiders.

What bore hole types are available?

All coupling types in this range are available with Y (long cylindrical bore, standard keyway), J (short cylindrical bore with counterbore), J1 (short cylindrical bore without counterbore), and Z (tapered 1:10 bore with counterbore for precision, zero-backlash fit). Bore diameters marked with an asterisk in the specification tables are compatible with both J and Z types. Always confirm the shaft-end geometry before ordering.

Need Help Selecting the Right Jaw Coupling?

Share your motor power, operating speed, shaft diameters, and application details — our engineering team will recommend the correct type, size, and spider grade and confirm availability within 24 hours.

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