Collet Basics

Where does it sit?

A collet (C) is used in a spindle motor (D), to clamp a cutting tool (A) to the end of the spindle taper (E). A nut (B) is used to compress the collet which applies a clamping force to the tool. 

A: Tool

B: Spindle nut

C: Collet

D: Spindle unit

E: Spindle taper

What the collet needs to do

Provide the maximum amount of clamping force

By clamping force, we mean the amount of grip the collet has on the tool. A high clamp force:

  • Dampens vibration

  • Allows for higher RPMs

  • Reduces chatter

  • Reduces risk of tool pulling out of the spindle

Provide the minimum run-out

By run-out, we mean the distance the tool mis-aligned from the center or rotation (shown below in red).

A low run-out value means:

  • All flutes do an even amount of work

    • Even wear

    • Better tool life

  • Better finishes

  • Better accuracy

  • Reduced wear in the spindle bearings

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