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<strong>Technical</strong> <strong>Information</strong><br />
<strong>Technical</strong> <strong>Information</strong><br />
Shrink Fit<br />
Shrink Fit<br />
The Concept<br />
HEAT<br />
Heat shrinking is not a new process in the machine tool industry. However,<br />
the concept was only recently implemented as a quick-change toolholding<br />
mechanism for clamping cylindrical cutting tools for high-speed machining<br />
applications.<br />
The Shrink Fit process begins by applying a quick and precise heat to the<br />
holding end of a toolholder. This causes the internal bore, which is slightly<br />
smaller than the shank of a cutting tool, to expand, allowing a tool to be<br />
inserted. As the toolholder cools, the bore shrinks to create 360° of uniform<br />
pressure along the entire length of the bore, resulting in an evenly distributed<br />
clamping force that mechanical toolholding cannot beat.<br />
Due to the design, flatted-style, Weldon ® , and Whistle Notch cutting tool<br />
shanks can employ Shrink Fit technology. To gain full benefits of the<br />
technology, fully cylindrical tool shanks are recommended. As long as the<br />
heating processes are kept within the elastic range of the toolholder material,<br />
this clamping operation can be repeated for several thousand cycles.<br />
HEAT<br />
HEAT<br />
toolholder body O.D.<br />
cutting tool shank<br />
clearance zone<br />
toolholder I.D.<br />
Shrink Fit Tooling Advantages:<br />
• Low runout — cutting tools are gripped 360° along the entire length of the<br />
cutting tool shank for an evenly distributed clamping force.<br />
• Clamping forces are greater than collets or hydraulic chucks.<br />
• During testing, tool material properties break down and shear before<br />
slippage occurs.<br />
• Slim and short toolholder profile designs are achievable because no moving<br />
parts are used.<br />
• Well suited for high-speed operations because their symmetry provides the<br />
best possible balance.<br />
• Sealing stop screws are not required — designed interference between the<br />
cutting tool and toolholder forms a seal that enables coolant to flow only<br />
through designated passages.<br />
These advantages enable Shrink Fit technology to work at greater speeds and<br />
feeds, produce better finishes, deliver increased tool and spindle life, and<br />
generate more productivity.<br />
M78 www.kennametal.com<br />
HEAT
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