What is the Shrinkage of the Heat Shrink Tool Holder?

In the world of CNC machining, precision, repeatability, and rigidity are critical for achieving high-quality parts. Among the many workholding and toolholding solutions available, Shrink Fit holders stand out as one of the most reliable methods for securing cutting tools. If you’ve ever wondered about the shrinkage process of a heat shrink tool holder, how it works, and why it matters, this article will walk you through everything you need to know.

Understanding Shrink Fit Technology

A Shrink Fit Holder is a type of high-precision CNC toolholder that uses thermal expansion and contraction to clamp cutting tools. The principle is simple yet effective:

• The inner bore of the shrink fit tool holder is manufactured slightly smaller than the tool shank.

• A shrink fit tool holder machine (or heat shrink tool holder machine) heats the holder, causing it to expand.

• The tool is then inserted into the expanded bore.

• As the holder cools, it contracts and “shrinks” onto the tool shank, creating a perfect interference fit.

This process ensures a 360-degree uniform clamping force, which minimizes runout and improves rigidity compared to conventional CNC collet holders.

How Much Does a Heat Shrink Tool Holder Shrink?

The amount of shrinkage in a heat shrink tool holder depends on the holder’s material, the heating temperature, and the bore size. Typically:

• Shrink fit holders are heated to about 280°C–320°C (536°F–608°F).

• This temperature allows the bore to expand just enough (a few microns) to insert the tool smoothly.

• Upon cooling, the holder shrinks back tightly, generating a powerful clamping force capable of holding the tool securely even at high spindle speeds.

This precise shrinkage is what gives CAT 40 Shrink Fit Tool Holders and other standards their excellent balance and performance, making them ideal for high-speed machining.

Benefits of Using Shrink Fit Tool Holders

1. Superior Runout Accuracy – Shrink fit tool holders typically achieve runout below 3 microns, improving tool life and surface finish.

2. Balanced for High RPM – Perfect for high-speed spindles in CNC machining centers.

3. Excellent Rigidity – Full 360° clamping improves rigidity compared to ER Collets or set screw holders.

4. Simple Tool Changes – Using a shrink fit tool holder machine, you can quickly heat and swap tools.

5. Reduced Vibration – Better balance means smoother cutting and less spindle wear.

Applications in CNC Machining

Shrink fit holders are widely used in industries requiring high precision and surface quality, including:

• Aerospace component machining

• Automotive mold and die production

• Medical device manufacturing

• High-speed and high-feed milling operations

Whether you are using CNC holders for drilling, end milling, or finishing passes, shrink fit tool holders offer consistent, repeatable results.

Maintenance Tips

To keep your shrink fit tool holder machine and holders in top condition:

• Regularly clean the bore to prevent dirt or chips from reducing clamping force.

• Avoid overheating beyond the recommended temperature range.

• Check tool shanks for wear and scratches before insertion.

• Balance your CAT 40 shrink fit tool holders if needed for ultra-high-speed applications.

The “shrinkage” in a heat shrink tool holder is what makes this system so reliable and precise. By using controlled thermal expansion and contraction, the toolholder achieves excellent clamping strength, high accuracy, and improved tool life. For shops seeking improved productivity and surface quality, switching to shrink fit tool holders and investing in a heat shrink tool holder machine is a wise choice.