Rigid Shaft Couplings
Built to Transfer Power.
Not Compromise.

What Is a Rigid Shaft Coupling — And When Should You Use One?

A rigid shaft coupling is a mechanical device that connects two rotating shafts end-to-end to transmit torque and rotational speed. Unlike flexible couplings, which incorporate elastomeric, metallic, or disc elements to absorb misalignment and vibration, a rigid coupling creates a completely fixed connection with zero relative movement between the two shaft ends. There is no slip, no damping, and no angular or radial compliance — what one shaft does, the other must do identically.

This characteristic makes rigid shaft couplings the correct choice wherever alignment can be guaranteed and where precise position correlation between driver and driven shafts is required. Pump-motor assemblies mounted on a common base plate and aligned by a competent millwright, servo-motor-to-leadscrew connections in CNC machines, and reactor agitator shaft extensions are all examples where rigidity is an advantage, not a liability.

Rigid vs. Flexible Coupling: The Core Trade-Off

The selection between rigid and flexible coupling types reduces to a single question: can you guarantee shaft alignment, or do you need the coupling to compensate for it? If your shafts are accurately aligned — within the angular and parallel tolerances the coupling manufacturer specifies — a rigid coupling delivers maximum torque density, zero backlash, and the longest service life of any coupling category. If misalignment is present and cannot be corrected at installation, a flexible coupling absorbs it and prevents bearing overload.

For a detailed comparison by application type, visit our application guidance page where we cross-reference coupling type against operating conditions.

Rigid Coupling Types — A Technical Overview

Flange Coupling (YL, YLD, GY, GYS, GYH Series)

The flanged rigid coupling is the most common shaft-to-shaft connection in industrial machinery. Two flanged hubs — one on each shaft — are bolted together face-to-face using precisely fitted bolts that transmit torque in shear. The YL/YLD series conforms to GB 5843-86 for torque ratings from 10 to 20,000 N·m; the GY/GYS/GYH series follows the updated GB/T 5843-2003 standard and covers nominal torques from 25 to 100,000 N·m. Hub bores accept Y-type straight bores with A-type keyways as the default, with J and J1 short-hub options available to reduce axial length where space is constrained.

Sleeve Coupling (GT Series)

The sleeve coupling — sometimes called a muff coupling or box coupling — is a single-piece cylindrical sleeve through which both shaft ends pass, with torque transmitted by a key or taper pin. It occupies the smallest radial envelope of any rigid coupling type and suits low-speed, light-load, smooth-running applications such as textile spindle drives and irrigation pump shafts. Shaft bore tolerance is H7; coupling material is typically 45# carbon steel for bores under 60 mm and cast iron for larger sizes.

Clamping Coupling (JQ Series)

The JQ clamping coupling is a split rigid coupling — two identical half-shells that clamp around both shaft ends and are drawn together by through-bolts. Its defining advantage is that installation and removal require no axial movement of either shaft, making it the correct choice for agitator shaft connections on enclosed reactor vessels where axial travel is obstructed. Torque transmission depends on bolt clamping force and the friction coefficient between shell and shaft; for non-standard output shaft diameters, specify the bore at enquiry stage.

Micro Rigid Coupling (TS7, TS7C Series)

Miniature rigid couplings for precision motion applications. The TS7 setscrew type uses two grub screws per hub to lock onto the shaft; the TS7C clamp type uses a slotted hub drawn closed by a single bolt, generating uniform radial clamping force without point loading. Both are available in aluminum alloy (standard) and 316 stainless steel (STS7, STS7C prefix) for corrosive environments. Moment of inertia figures are calibrated at maximum shaft bore — consult the datasheet when calculating servo motor inertia ratios.

Locking Assembly (TS7Z Series)

The TS7Z locking assembly is not a shaft-to-shaft coupling in the conventional sense — it connects a hub to a shaft by generating radial pressure through tightening bolts that advance a two-ring conical taper mechanism. This eliminates keyways and their associated stress concentrations, distributes clamping load evenly around the shaft circumference, and achieves higher torque density than equivalent keyed connections. Applications include gearbox output hubs, sprocket mounting, and anywhere a hub-to-shaft joint is more appropriate than a shaft-to-shaft bridge.

Oldham (Sliding-Block) Coupling (SL, WH Series)

Technically classified alongside rigid coupling types for their lack of elastomeric elements, Oldham couplings use a three-piece sliding-block mechanism to compensate for parallel shaft offset. The SL series (cross-sliding block) handles radial offset up to 8.0 mm at OD 460, with nominal torques reaching 63,000 N·m. Maximum operating speed is 70–250 rpm, making this type unsuitable for high-speed drive applications. The WH sliding-block coupling covers lighter torques with improved shock absorption for rough drive conditions.

Material Selection for Rigid Couplings

Standard flange and sleeve couplings are produced in gray cast iron (HT200) for cost-sensitive applications and in cast steel or 45# forged steel where higher torque density or impact resistance is needed. Weight and rotational inertia figures in our datasheets are calculated for cast iron at minimum bore; steel variants are heavier and carry proportionally higher inertia — account for this when sizing motor starting torque for high-inertia loads. For food, pharmaceutical, and coastal environments, stainless steel micro couplings (STS7, STS7C prefix) are the specified option.

How to Select a Rigid Shaft Coupling

Start with three parameters: the nominal torque your application produces (in N·m), the operating speed (in rpm), and the shaft bore diameters on driver and driven sides. Cross-reference these against the coupling series tables to identify the size code that satisfies all three. Then verify that the bore range for that size includes your actual shaft diameter — if it does not, move to the next series size. Finally, confirm that the coupling's L0 dimension (total axial length) fits your available space between shaft ends.

If you are working through a selection for the first time or have an application with non-standard parameters, contact our technical team at [email protected] — we will work through it with you.