1. What applications use heat shrink tubing? The primary uses for heat shrink tubing are:

• Seal water and dust out of cable splices
• Insulate cables and wires against extreme heat in aircraft, boats, and military vehicles
• Provide a barrier between cables and corrosive chemicals
• Color code cables for easy identification
• Harness multiple wires together
• Make long-lasting labels for network patch cords
• Neatly terminate the ends of braided sleeving
• Improve the look of cables in computer case mods or custom cars and motorcycles

2. What is the difference between heat shrink tubing and cold shrink tubing?

Cold shrink comes stretched over a removable core, allowing you simply to slide the tube over the
splice or termination and unwind the core, letting the cold shrink tube contract to fit snugly over the
cable. Heat shrink requires a heat source, usually a torch or an electric heat gun, to shrink it over the
splice or termination. Heat shrink typically requires more skill to prepare and apply.

3. How do I determine the proper size shrink tube?

A practical approach to determining the size of tubing to use is simply to use one that will shrink to
about 70% of the minimum supplied I.D. For example, to cover a cylinder of diameter ¾-inch, a
tubing with a minimum supplied diameter of 1-inch should be used. To cover a ½-inch bar, a
¾-inch tube should be used. Now, for this latter case a 2:1 shrink ratio tubing could be used if one
wished to maximize the recovered wall thickness.

4. What is the percent shrinkage?

Typically 15% from the minimum expanded inside diameter.

5. How do I get more than 15% shrinkage?

Whenever very high radial shrinkage (up to 50% or more) is required, the "Drawing Process" can
be used. This simply requires axial tension and stretching of the tube while it is being heated. Over
50% diameter reduction can be achieved at temperatures below 100°C (212°F). Higher diameter
reductions can be achieved at higher temperatures, up to about 190°C (374°F).

6. How do I minimize axial shrinkage?

By either choosing a tubing size that more closely fits on to the product to be covered (start with a
small tube size) or hold/restrain the ends of the tube during the shrinking process to prevent the tube
from shrinking in length.

7. What does the term "minimum supplied diameter" mean?

This refers to the inside diameter, or I.D., of the tubing as supplied by the manufacturer. Typically it
reflects a minimum value so that the tubing will readily slide over the object to be covered. In the
case of tubing that is supplied as a ½-inch, minimum supplied I.D. and a 2:1 recovery (this means
it shrinks to about one-half of its supplied size), the supplied tubing is always supplied with a
minimum I.D. of 0.500-inches.

8. What does the term "maximum recovered I.D." mean?

This refers to the final inner diameter of the tubing after the tubing has been fully shrunk, or recovered,
through the careful application of heat. A maximum value is specified to ensure that the tubing will fit
snuggly about the object being covered. In the case of a tubing that is supplied as ½-inch minimum
supplied I.D. tubing, with a 2:1 shrink ration, the recovered I.D. will always be 0.250-inches. While
this tubing may "recover" to fit a 0.240-inch item snuggly, it will always recover to provide a snug fit
to an object 0.250-inches.

9. What happens to the tubing wall thickness when the tubing is recovered?

After recovery, the tubing wall thickness increase to some extent. Because of some variability, the
recovered wall thickness is generally specified as a nominal value.

10. How do I know what is the best FIT® Heat Shrinkable Tubing material to select for my
application?

Once the application and environmental conditions are understood, then the proper tubing material may
be selected.

11. What is the best way to shrink your FIT® Heat Shrinkable Tubing?

          A. Select the proper size of heat shrink tubing for your project. In order to get a
              secure fit, be sure that the tubing’s recovered diameter (the diameter after
              shrinking) is smaller than the diameter of the area you’re going to insulate.

         B. Cut the heat shrink tubing to a usable length, and be sure to allow for a
             minimum 1/4" overlap over any existing insulation or connectors. Keep in
             mind that tubing also shrinks lengthwise…typically 5-7% during the shrinking
             process.

         C. Slide the cut tubing over the object that you’re covering; if you’ll be splicing,
             slide the tubing over the center of the splice, and allow for equal overlap on
             both sides.

         D. Before shrinking, check your tubing’s specifications for the recommended heating
             temperature. Any commercial heat gun or heat shrink oven can be used to shrink
             the tubing. Since uncontrolled heat can cause uneven shrinkage, physical damage
             and insulation failure, the use of open flame is not recommended.
 
         E. If you’re covering a long length of cable with tubing, begin shrinking at one end,
             and gradually work your way down to the other. To ensure that the tubing shrinks
             evenly and without air bubbles, rotate the project as you’re applying heat.
 
         F. Evenly apply heat over the length and around the diameter of the tubing,
             until it is uniformly shrunken and conforms to the shape of the cable, hose, or
             splice that it’s covering. Immediately remove the heat source, and allow the tubing
             to cool slowly before you apply physical stress to it.

        G. Avoid overheating the heat shrink tubing, because it will become brittle and/or
            charred.

Tip!  Silicone lubricant spray can be applied to wires or cords to guide heat shrink over them without
compromising the heat shrink material.