Heat Shrink Tubing Sizes

 

Heat shrink tubing is a simple tool used in all sorts of electrical and mechanical projects. 

When heated, color-coded heat shrink tubing decreases in diameter or shrinks tightly around wires or whatever is put inside the tube. 

This "shrinking" allows it to protect wires from damage, keep them insulated, and even bundle them together neatly, making organization and consolidation a breeze.

However, if your heat shrink tubing is too big or small, it will not work correctly and could damage your wires, leading to further risks down the line. 

That is why we created this guide—to help you understand how heat shrink tubing sizes work and ensure you get the right fit for your projects.

What Is Heat Shrink Tubing?

Heat shrink tubing is a flexible material typically made from polyolefin, fluoropolymer, or similar materials. It comes in various diameters and shrink ratios. 

When heated using a heat gun or other heat source, the tubing shrinks tightly around the object it covers, making it useful in a variety of scenarios and industries. 

Here are some ways in which heat shrink tubing is used: 

• Insulation

Heat shrink tubing prevents electrical shorts and protects against electrical shocks by covering exposed wires. 

It acts as a barrier that keeps electrical components safe and functional and protects users from getting electrocuted.

For example, it insulates wires, creates strain relief, and even waterproofs electrical connections in the electronics and automotive industries.

• Protection

The tubing shields wires from physical damage, such as abrasion, and environmental factors, such as moisture, dust, and chemicals. 

This makes it ideal for safeguarding your electrical connections in harsh conditions. One example of this is in marine industries, where they protect electrical components from moisture, salt spray, and corrosion.

• Bundling

Heat shrink tubing keeps your wiring neat and organized by bundling multiple wires together. This prevents tangles and makes projects look professional and easier to manage. 

It is a lifesaver in applications like aeronautics, where it keeps delicate wires like those found inside airplanes lightweight, organized, and secure.

How to Measure Heat Shrink Tubing

First, make sure you have your calipers ready. These tools are vital for nailing the exact diameter of cables or whatever object you plan to use heat-shrink tubing for. 

No calipers on hand? A ruler or measuring tape can be used as an alternative.

Here are the steps for accurately measuring heat shrink tubing.

1. Measure the Diameter of the Object 

Grab those calipers and measure the fattest parts of the cable and not just one spot. This step is critical to ensure you do not end up with a size too small or lose the snug fit you are aiming for.

NOTE: Wires can be wonky, so ensure the heat shrink tubing can handle any bulges that will arise.

2. Determine the Unshrunk Diameter

Here is where you pick the right size tubing. You will want something a tad larger than the object’s diameter.

NOTE: aim for a tubing size that is about 25% bigger. 

This size difference guarantees a tight fit once the tubing contracts. 

3. Identify the Shrunk Diameter

Use a heat shrink size chart to determine the shrunk diameter of the tubing. This will help you find a tubing size that will fit snugly around your object once it has been shrunk.

4. Consider the Shrink Ratio

The tubing's shrink ratio indicates how much it will shrink when heated. 

A 2:1 ratio means it shrinks in half, while a 3:1 shrinks to a third. 

Check a heat shrink size chart to see the final shrunk diameter and make sure it matches your needs.

Heat Shrink Tubing Sizes

Heat shrink tubing comes in a wide range of sizes, typically denoted by their diameter before shrinkage. 

It is also characterized by its shrink ratio, which indicates how much the tubing shrinks in diameter when exposed to heat. 

Common shrink ratios include:

Shrink Ratio	Original Diameter	Shrunk Diameter	Description
2:1	50.8mm (2")	25.4mm (1")	This means the tubing shrinks to half its original diameter when heated. General applications
3:1	24.0mm (1")	8mm (1/3")	Significant size variations
4:1	32.0mm (1.25")	8mm (1/3")	Extreme size variations

 

Remember: This chart only serves as a general guideline. The specific size and shrink ratio you need will depend on your application and the heat shrink tubing itself. 

Choosing the Right Size

Selecting the correct heat shrink tubing size ensures effective insulation and protection. 

Here is a straightforward guide to help you choose the right size for your needs.

Fit

The tubing should fit snugly around the object after shrinking. 

Using tubing that is too small will not provide proper insulation or protection, while overly large tubing will bunch up and may not shrink evenly. 

As a rule of thumb, choose a heat shrink tubing size 20-30% larger than the diameter of the object you are covering before shrinkage. This ensures a tight fit after shrinking. 

For applications needing a very snug fit, opt for a tubing size that is only 10-15% larger than the object's diameter.

Material

Different materials have varying shrink ratios. 

Consider the material of the heat shrink tubing and choose a size that complements its shrink properties. 

Tubing with a larger shrink ratio, like 4:1, offers more flexibility in accommodating a wider range of object diameters.

Also, using high-quality polyolefin is the best choice for most applications. 

It is durable, flexible, and provides a reliable, waterproof connection, making it perfect for outdoor projects, marine applications, and automotive repairs.

Environmental Factors

If the tubing will be exposed to extreme temperatures or harsh environments, select a material and size that can withstand those conditions. 

As mentioned above, a high-quality polyolefin is a great choice. 

Not only is it resistant to fire, water, and voltage, but it is also versatile and suitable for a variety of uses—from aircraft and boats to military-grade vehicles.

Applications of Different Sizes

Heat shrink tubing is incredibly versatile, and its range of sizes makes it perfect for various tasks across different industries. 

Here is how different sizes can be put to use.

1. Small Sizes (1.0 mm–4.0 mm diameter)

These are great for delicate and precise jobs, such as the following: 

• Electronics: Insulating small wires, component leads, LED legs, and delicate electronic components.
• Jewelry Making: Creating decorative accents on wires and clasps.
• Hobby and Craft Projects: Finishing edges of wires, providing strain relief for delicate connections.

2. Medium Sizes (4.0 mm–8.0 mm diameter)

Medium-sized tubing is perfect for more robust applications, such as:

• Automotive: Insulating and protecting wiring harnesses, battery terminals, and electrical connectors.
• Marine: Shielding electrical components on boats and marine equipment from moisture, salt spray, and corrosion.
• Appliance Repair: Insulating wires and connections within appliances.

3. Large Sizes (8.0 mm diameter and above)

When it comes to heavy-duty jobs, large heat shrink tubing should be your go-to.

• Industrial Applications: Protecting high-voltage cables, bus bars, and other large electrical components in power distribution systems.
• Aerospace: Offering lightweight insulation and strain relief for critical electrical systems in aircraft.
• Telecommunications: Insulating and bundling coaxial cables for data and signal transmission.

Installation Tips

Proper installation ensures a snug fit and long-lasting protection. 

For optimal results, follow these practical tips when installing heat shrink tubing. 

Here is a step-by-step guide to help you get it right.

1. Preparation 

Ensure the object to be covered is clean, dry, and free of contaminants such as dirt, oil, or grease. 

These contaminants can affect the heat shrink tubing’s ability to adhere properly, potentially leading to poor insulation or protection. 

Use a clean cloth and appropriate cleaning agents to wipe down the object thoroughly, as a clean surface allows for a strong and long-lasting bond.

2. Cutting the Tubing

Now that your workspace is prepped, it is time for the tubing itself. Use sharp scissors or a dedicated heat shrink cutter for a clean, precise cut. 

Remember, the tubing will shrink down, so leave a small allowance on each end to ensure complete coverage after heating.  

Ideally, you want about 1/16th to 1/8th of an inch extra on either side for optimal results.

3. Sliding the Tubing

Slide the tubing over the object, ensuring it is positioned correctly before applying heat. 

For smaller objects or intricate applications, you might need to use tweezers or needle-nose pliers to position the tubing accurately. 

This step is crucial to ensuring that the tubing covers all required areas and does not shift during heating. 

Proper positioning helps achieve even shrinking and better protection.

4. Heat Application

Use a heat gun set to the appropriate temperature recommended for the specific heat-shrink tubing material. 

Start with low heat settings and gradually increase if needed. 

Apply heat evenly, moving the heat gun constantly to avoid overheating or melting the tubing. Avoid applying direct heat to the object itself, as this could damage it. 

The key here is to be patient and apply the heat slowly, allowing the tubing to shrink evenly without bubbling or scorching.

5. Shrinking Process

Observe the tubing as it shrinks. It will conform to the shape of the object and become snug around it. 

Ensure proper ventilation when using a heat gun, as fumes may be released during heating. 

For larger heat shrink tubing sizes, consider using a heat shrink tunnel for more uniform and efficient heating. 

This step is critical for achieving a tight fit and ensuring the tubing provides effective insulation and protection.

6. Inspection

Once the tubing has shrunk, inspect it carefully for any wrinkles, gaps, or signs of overheating. 

If necessary, re-apply heat to address any imperfections. 

A thorough inspection helps identify any areas that might need additional attention to ensure a secure fit.

Frequently Asked Questions (FAQs)

Below are some common questions related to heat shrink tubing sizes. 

What Size Heat Shrink Tubing Do I Need?

Select tubing 20-30% larger than the measured diameter to ensure a snug fit after shrinking. 

Determining the correct size begins with measuring the diameter of the materials to be covered. 

How Do You Measure Heat Shrink Tubing Size?

If available, measure the width of the flattened piece with calipers. Multiply the width by 2, then divide by 3.1416 (pi) to find the diameter of the tubing. 

This ensures you select tubing that will fit appropriately after shrinking.

How Tight Should Heat Shrink Be?

After shrinking, the heat shrink tubing should create a secure and tight fit around the object. The tubing's shrunk diameter should ideally be slightly smaller than the object's (or the wire’s) diameter. 

Key Takeaways on Heat Shrink Tubing Sizes

With this heat shrink tubing sizes guide under your belt, you are now equipped to tackle heat shrink tubing installation like a pro! 

Here is a quick recap of the key points covered in this article:

• Importance of Size: The right size ensures proper insulation, protection, and strain relief for your wires and components.
• Measurement: Accurately measure the object's diameter before shrinkage.
• Shrink Ratios: Understand the shrink ratio (2:1, 3:1, etc.) of the chosen tubing to determine how much it will shrink.
• Size Selection: Choose tubing 20-30% larger than the object's diameter for a snug fit after shrinkage.

Heat shrink tubing’s versatility is critical to maintaining electrical safety and dependable functionality across many industries, from DIY electrical repairs to complex work on military vehicles.