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This article will show you how to expand electrical-insulating heat shrink tubing by stretching it. [1] X Research source
Steps
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Select the right tool for the size of the heat shrink tubing you want to expand.
Most smaller tubing is easy to stretch with needle-nose pliers. If possible, find a pair with extended ends to accommodate longer sections of tubing. [2] X Research source -
To stretch larger tubing, use a combination of two pliers to expand the tubing as shown in this illustration.- Extremely small tubing calls for tweezers with needlepoint tips, such as LTD's Tweezerman models.
Advertisement - Extremely small tubing calls for tweezers with needlepoint tips, such as LTD's Tweezerman models.
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Insert the tweezers or pliers into the tubing as far as possible. Make sure the tool used is completely closed. -
Pull the pliers apart slowly to open up the ends. If using tweezers, use a jeweler's screwdriver to help pry the tweezers apart. -
Stretch the tubing only a little at a time to avoid tearing or puncturing it. -
Close the tweezers or pliers and rotate the tubing slightly. -
Repeat steps 2 through 5 until you have rotated the tubing enough to return to your starting point. [3] X Research source -
Flip the tubing to so that the other end of it fits over the tweezers or pliers, and repeat the above steps. -
The tubing is now ready for use.
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Expert Q&A
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QuestionWhat's the right way to put heat shrink tubing on a wire?Marvin Woo is a licensed electrician and the Owner of Woo's Electrical & Appliance based in East O’ahu. With over two decades of experience, he specializes in troubleshooting issues and maintaining residential electrical systems. Marvin is both licensed and insured to complete electrical work in the state of Hawaii.Place the section of heat shrink tubing onto your wire before you actually fuse it on. Once in place, center the heat shrink tubing on the wire and use a heat gun to apply heat to all sides of the tubing, which will evenly shrink it.
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QuestionHow do I know if I have heat shrink tubing that's the right size for my wire?Marvin Woo is a licensed electrician and the Owner of Woo's Electrical & Appliance based in East O’ahu. With over two decades of experience, he specializes in troubleshooting issues and maintaining residential electrical systems. Marvin is both licensed and insured to complete electrical work in the state of Hawaii.Generally, heat shrink tubing should be just slightly larger in diameter than the wire you want to insulate so that it's easy to slip on. When you heat the heat shrink tubing, it will then fit perfectly around your wire.
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Tips
- Stretched/expanded tubing will shrink much faster, using less heat, than an equivalent piece of tubing that has not been stretched.Thanks
- Use the following for determining safe dielectric withstanding voltages when expanding heat shrink tubing: For every mil (1/1000 of an inch) in thickness, typical Polyolefin heat shrink tubing (MIL-DTL-23053/5, Class 1 and 3 specification), with a standard wall thickness tolerance of ± 20%, will have a dielectric withstanding voltage of 500 volts . The smallest available heat shrink tubing has a thickness of 0.2 mil, even though most sizes are around 1 mil. For the smallest heat shrink tubing, expanding it to double its size may reduce its thickness by up to 50%, which is 0.1 mil. Multiple this by its withstanding voltage of 500V/mil, and the smallest heat-shrink tubing will still withstand 50V. However, when the tubing is heat-shrunk, its thickness will increase, which will in turn increase its overall dielectric withstanding voltage.Thanks
- Good-quality tubing can expand to more than twice its size. Stretching as described above should not puncture or tear it.Thanks
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Warnings
- Be gentle with delicate tweezers. Using any metal object to pry them apart, as in the illustrations above, can damage them.Thanks
- Be careful when cutting off sections of the sleeving. If the cut is uneven or jagged, that will make the tubing more susceptible to tearing when stretched.Thanks
- Expanding any tubing beyond its original size changes its thickness and may affects its dielectric withstanding voltage. If your project or application of expanded tubing is already within close tolerances, test an expanded section of tubing first, in a safe, controlled environment.Thanks
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References
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Reader Success Stories
- "I needed to repair a cable insulation on a medical device with a connector that was much larger than the cable diameter. With this technique, I managed to widen a narrow piece of shrink tube to slip over the connector and then effect the repair." ..." more
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"I needed to repair a cable insulation on a medical device with a connector that was much larger than the cable diameter. With this technique, I managed to widen a narrow piece of shrink tube to slip over the connector and then effect the repair."
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