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 U37R CPLG 3/8X3/8 N/KW W/SS

Hub Style

N/A Regular


N/A Shaft-to-Shaft


N/A Steel


N/A 0.27 lb


N/A Gray/Metallic

Bore Type

N/A Finished Bore

Dimensional Data

Bore Size   

N/A 3/8 x 3/8 in

Hub Size

N/A U37R

Set Screw Thread Size (Dimension T)

N/A 10-24

Keyway Size (W x D)

N/A No Keyway

Dimension HD

N/A 0.860 in21.84 mm

Overall Length

N/A 2.060 in52.32 mm

Pin Location (Dimension SL)

N/A 0.250 in

Length thru Bore

N/A 0.520 in13.21 mm

Min. Bore (Dimensions ID1/ID2)

N/A 0.250 in6 mm

Max. Bore (Dimensions ID1/ID2)

N/A 0.375 in9.53 mm

Cubic inches

N/A 1.52358 in³

Performance Data

Operating Temperature Range

N/A -40 to 250 ºF

Max. Torque

N/A 39.00 in·lb

Max. Speed

N/A 30000.00 rpm

Axial Misalignment (∆ Ka)

N/A 0.020 in0.51 mm

Max. Parallel Misalignment

N/A 0.014 in0.36 mm

Wind-Up Angle at Nominal Torque

N/A 1.78 º

Wind-Up Angle at Max. Torque

N/A 4.5 º

Rated HP at 100 rpm

N/A 0.06 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.