Shrink Fit Holders

Shrink fit tool holders are highly precise and well-balanced tool holders that are ideally suited for high-speed machining, multi-axis machining, finishing milling, and drilling. Their slim design and extended reach enable tool use in tight and complex machining environments, such as mold making and multi-axis machining centers.

Operating Principle of Shrink Fit Holders

The operation of a heat shrink tool holder is based on the phenomenon of thermal expansion. The tool is secured in the holder using a separate heat shrink unit, which inductively heats the holder to approximately 450–500 °C. At this temperature, the holder’s sleeve expands, allowing for the tool to be inserted. As the holder cools, it contracts tightly around the tool shank, forming an extremely precise and rigid connection without moving parts or tightening mechanisms.

Heat shrink units may come with optional air or liquid cooling systems that rapidly cool the holder down to its operating temperature. Protective gloves should always be used when handling tools, as the temperature in the shrinking area of the holder can be extremely high.

Features and Advantages of Shrink Fit Tool Holders

• Exceptional runout accuracy, typically less than 3 µm
• Outstanding balance, suitable for high-speed machining (HSC)
• Slim and symmetrical design, excellent reach and rigidity
• Compatible with most tool shanks, such as smooth shanks compliant with DIN 6535 HA / HB / HE standards
• High torque and clamping force transfer, up to several hundred newton-meters (e.g. Ø20 mm holder: 420 Nm, Ø32 mm holder: 850 Nm)
• Fast and secure tool changes with the heat shrink unit

Applications of Shrink Fit Holders

Heat shrink tool holders are primarily intended for machining operations requiring precision and balance, including:

• High-speed and finishing milling
• Drilling
• Multi-axis and mold machining
• Light and medium-duty roughing
• For heavy roughing, reinforced heat shrink holders are available. However, standard slim holders are not recommended for heavy loads, as their thin construction does not provide enough support for high cutting forces.

Safety and Maintenance for Shrink Fit Holders

Using heat shrink holders requires that:

• The holder is completely cooled before reheating
• The minimum tool clamping depth is achieved
• The user is technically trained and follows the manufacturer's instructions
• Only compatible tool shanks are used (tolerance class h6)

For maintenance, the holder should be:

• Cleaned and oiled during storage
• Inspected for possible damage or wear
• Kept in a dry environment to prevent corrosion

Summary

The shrink fit tool holder is an affordable, accurate, and reliable tool holding solution for modern machining. It offers excellent runout accuracy and dynamic balance, making it a popular choice for finishing, high-speed, and multi-axis machining. When used and maintained correctly, a heat shrink tool holder is a long-lasting and highly efficient tool holding option.