U Type Shaft-to-Shaft
    The U Type is the basis for all Uniflex couplings. It is a shaft-to-shaft flexible coupling with a simple one piece design, making it ideal for indexing, robotic or positioning applications. The U Type consists of a triple-wound flexible steel spring brazed to a steel hub at each end. This all steel design ensures optimum equipment protection in severe environments and/or high temperature applications. Regular and short versions are available for most sizes to accommodate different overall length requirements. Special hub or bore modifications are also possible. These units can be supplied with either pin holes or with keyways and set screws. Lovejoy does not recommend the reboring of uniflex couplings by customers due to potential damage to the brazed joint.
    This is a durable one-piece flexible coupling for general purpose shaft-to- shaft applications. It is the basis for all Uniflex coupling types.
Unit of Measure



N/A U137S CPLG 1-3/8X1-3/8 5/16KW

Hub Style

N/A Short


N/A Shaft-to-Shaft


N/A Steel


N/A 4.00 lb

Weight (Complete Coupling w/ Max. Bores)

N/A 4.00 lb


N/A Gray/Metallic

Bore Type

N/A Finished Bore

Dimensional Data

Bore Size   

N/A 1 3/8 x 1 3/8 in

Hub Size

N/A U137S

Set Screw Thread Size (Dimension T)

N/A 3/8-16

Keyway Size (W x D)

N/A 5/16 x 5/32 in

Dimension HD

N/A 2.54 in64.52 mm

Overall Length

N/A 4.120 in104.65 mm

Pin Size

N/A 0.375 in

Pin Location (Dimension SL)

N/A 0.69 in

Length thru Bore

N/A 1.010 in25.65 mm

Min. Bore (Dimensions ID1/ID2)

N/A 0.625 in16.00 mm

Max. Bore (Dimensions ID1/ID2)

N/A 1.375 in34.93 mm

Cubic inches

N/A 26.58059 in³

Performance Data

Operating Temperature Range

N/A -40 to 250 ºF

Max. Torque

N/A 1260 in·lb

Max. Speed

N/A 6000 rpm

Axial Misalignment (∆ Ka)

N/A 0.020 in0.51 mm

Max. Parallel Misalignment

N/A 0.350 in0.89 mm

Wind-Up Angle at Nominal Torque

N/A 1.35 º

Wind-Up Angle at Max. Torque

N/A 3.00 º

Rated HP at 100 rpm

N/A 2.02 hp

# of Set Screws Required per Hub

N/A 1

Coupling Design

Coupling Design

N/A Flexible Spring Type Coupling with Exclusive Triple Wound Spring Design
    The Uniflex Coupling is an all steel, single piece coupling that solves a variety of application concerns including: high misalignment, space limitations, high temperature, and exceptionally low backlash/windup. The unique flexing center of the Uniflex consists of three opposingly wound square wire springs for forward or reverse operation. Two steel hubs are then brazed to the steel spring pack to create a durable one-piece flexible coupling.



  • Total backlash is approximately 1/3 of windup at maximum torque – consult Lovejoy Engineering for more information.
  • OAL Tolerance: + 1/8 inch.