What Causes a Flexible Shaft to Coil Up?

When a flexible shaft becomes tangled or resists forward motion, it’s usually due to one of two causes. Identifying the right one will help you adjust your approach and keep everything running smoothly.

1. Flexible Shaft Coiling or Tangling Before the Pipe

If the shaft begins to twist or coil outside the pipe—before entering—it’s often due to excess rotational inertia. As the shaft spins, it stores energy. If that energy isn’t properly managed, the exposed section may loop or whip unpredictably.

This typically happens when the shaft isn’t stabilized, guided correctly, or is rotating too fast without enough tension or control at the entry point.

2. Stiffness or Spiraling Inside the Pipe

If the shaft has already entered the pipe and then becomes hard to push—or begins spiraling inside—it’s likely because the shaft is too thin for the pipe’s diameter.

For instance, inserting a 6mm (¼ inch) flexible shaft into a 150mm (6-inch) pipe may seem okay at first. But after some distance, the shaft can start following the inner circumference of the pipe rather than advancing in a straight line. This buildup of coiling makes it harder to push further and can lead to blockages or reduced performance.

The Solution

To avoid both scenarios, ensure that your shaft size matches the diameter of the pipe. A larger-diameter shaft provides better stiffness and directional control in wide pipes, making it less prone to spiraling or tangling.

Quick Reference:

• Tangling before entry: Likely caused by excess inertia and lack of guidance
• Jamming or spiraling inside: Shaft diameter too small for the pipe

Use the right shaft for the job, and you’ll get smoother, more reliable operation.

For a more visual explanation, please take a look at this video.