Flexible Shafts Information



Flexible shafts provide rotary power transmission along curved or adjustable axes. They are used in a wide variety of remote control, valve actuation, and power transmission applications. 


Types of Flexible Shafts


There are two basic types of flexible shafts:Flexible Shafts


  • Unidirectional shafts rotate in a clockwise or counterclockwise direction as viewed from the motor or drive-end of the shaft. They are used for power transmission along non-linear axes in industrial automation, heavy-duty, and specialized applications such as agricultural equipment, speedometers, dentistry, woodworking, and jewelry tools.
  • Bidirectional flexible shafts can be rotated in either direction or reversed. They are well-balanced in both directions and suitable for cyclic applications. Some flexible shafts are corrosion resistant or can withstand environmental contaminants such as dust, fluid, and oil. Others have a casing around the shaft for protection and safety.


Specifications for flexible shafts include


  • Maximum speed
  • Torque capacity
  • Diameter
  • Minimum bend radius
  • Length, stiffness
  • Torsional deflection
  • Axial stretch

 Maximum speed is the maximum, rated rotational speed under load. Units of measure includeFlexible Shafts


  • Revolutions per minute (rpm)
  • Revolutions per second (rps)
  • Revolutions per hour (rph)

Some Important Measurements for selection are:


  • Torque capacity is the maximum, continuous torque transmission for which flexible shafts are designed. Torque, the measure of force applied to a member to produce rotation, is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.
  • Shaft diameter includes the shaft casing and helps determine speed and torque requirements.
  • Minimum bend radius is measured during shaft operation.
  • End-to-end length is measured along the centerline of the shaft. 

Applications and Materials



Flexible shafts differ in terms of materials and applications. Most products are made of


  • Carbon steel
  • Stainless steel
  • Tempered steel
  • Music wire
  • Rocket wire
  • Bronze alloys
  • Copper alloys

Aerospace ApplicationsFlexible Shafts


The aerospace industry uses flexible shafts in


  • Thrust reverser actuation
  • Variable bleed valve
  • Magazine drive shaft
  • Rescue pump
  • Scavenger pump
  • Flap actuation systems.

Automotive Applications


Automotive applications include


  • Automatic pedal adjustment,
  • Sliding door adjustments, a
  • Power seating tracks

Industrial and Medical


Flexible shafts are also used in industrial power tools and reach rods for valve removal. In the medical field, flexible shafts are used in


  • Biopsy probes
  • Magnetic resonance imaging (MRI) drug delivery
  • Orthopedic instruments
  • Eye surgery.

Related Standards


DIN 75532-2 - Transmission of rotary motions; flexible drive shafts

DIN 75532-1 - Transmission of rotary motions; types of connection to gears, intermediate gears, flexible gears, fexible drive shafts and equpment

JIS D 5602 - Flexible shafts for speedometers and tachographs of automobiles




Image Credits:


Berg W.M., Inc. | CEF Industries, LLC | S.S. White Technologies, Inc.




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