Torsion springs store energy by twisting and produce torque in response to rotational movement. The ends of a torsion spring, often called legs, are critical to how the spring mounts and how torque is transferred into the assembly.

The shape, angle and length of the ends directly affect fit, performance and service life.

Straight Leg Ends

Straight legs extend directly from the coil with no additional bends.

They are simple and cost effective and work well when the spring locates into slots, holes or against flat surfaces. Straight legs are best suited to applications with clear, direct mounting points and minimal space constraints.

Angled or Offset Leg Ends

Angled legs are bent to a specific angle relative to the spring body, such as 90°, 180° or 270°.

They allow the spring to engage with components positioned at different orientations and are useful where a straight leg would not align with the mechanism. Angled ends should use smooth bend radii to avoid excessive stress and reduced fatigue life.

Tangential Leg Ends

Tangential legs exit the spring following the curve of the coil.

This provides a smooth transition from coil to leg and helps reduce stress concentration. Tangential ends are often used where clearance is tight or where the spring rotates through a wide range of motion.

Radial Leg Ends

Radial legs extend outward perpendicular to the spring body.

They are commonly used when torque needs to be applied into holes, slots or rotating components such as hinges and levers. Radial ends offer a strong mechanical connection but must be carefully aligned to prevent binding.

Choosing the Right End Type

The correct end type depends on how the spring mounts, how torque is applied and the available space within the assembly. Leg geometry should avoid interference with nearby parts and should be designed with fatigue life in mind.

In all cases torsion springs should be designed to tighten under load rather than unwind, as this improves durability and reliability.

Best Practice

End design should be kept as simple as possible while meeting functional requirements. Complex bends increase cost and stress. Smooth transitions and adequate leg length help ensure consistent torque and long service life.

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