Why Fish Tape Is Difficult to Push Through Bends in Conduits

Fish tape is widely used for pulling wires through electrical conduits, but operators often encounter difficulty when navigating bends or curves. Understanding the mechanical and physical factors that contribute to this challenge is essential for proper tool selection and installation techniques.

1. Increased Friction at Bends

As the tape passes through a curved section of conduit, the contact area between the tape and the inner surface increases.

Frictional resistance grows with tighter bend radii, making it harder to push the tape forward.

The effect is magnified in long conduit runs or when multiple bends are present.

2. Rod Stiffness vs. Flexibility

Fish tape must balance flexibility to navigate bends and stiffness to transmit pushing force.

Too stiff a tape may bind against the outer wall of the bend, while too flexible a tape may buckle or coil, reducing forward movement.

The mismatch between tape properties and conduit geometry is a primary reason for difficulty in bends.

3. Conduit Surface Roughness

Rough, corroded, or debris-filled conduits increase resistance in bends.

Sharp edges or burrs at conduit junctions can catch the tape, causing it to stall.

Accumulated dirt, mud, or previous cable remnants exacerbate friction and obstruction.

4. Kinking or Twisting of the Tape

Pushing tape through a bend can induce torsional stress, leading to kinks or twists.

Twisting increases internal resistance, and the tape may fold back on itself, preventing further progress.

5. Lubrication Deficiency

Lack of appropriate wire-pulling lubricant increases friction, particularly at curves.

Proper lubrication reduces the contact resistance between the tape and conduit, allowing smoother advancement.

6. Load and Push Technique

Excessive pushing force may cause the tape to buckle, while insufficient force prevents it from reaching the end of the bend.

A steady, controlled push combined with slight rotation of the tape often helps navigate curves.

Conclusion

Fish tape is difficult to push through bends due to increased friction, tape stiffness limitations, conduit surface roughness, kinking, and insufficient lubrication. Proper tape selection, conduit inspection, use of lubrication, and careful pushing technique can significantly improve performance and reduce the risk of tape damage or stalling.

References

National Electrical Contractors Association (NECA). NECA Wiring Methods Manual, 2020.

Bartley, J., & Fisher, R. Utility Installation Tools Handbook. McGraw-Hill, 2018.

Gibson, R. (2019). “Mechanical Behavior of Fish Tape in Curved Conduits.” Journal of Electrical Installation Technology.

IEC 60364-5-52 – Selection and Erection of Electrical Equipment – Wiring Systems.