Maintaining your tool holder and collet

The tool holder and collet are critical parts of the machine that are often overlooked for maintenance. We will discuss the parts of the collet and nut style tool holders, also how to look out for wear and tear.

Parts of the tool holder include:

ColletTaper – conical shaped area of the tool holder that enters the spindle when changing the tool

Pull studs – screws into the top portion of the taper

V-flange – part of the tool holder that the automatic tool changer locks into when moving the tool from the tool changer to the spindle and vice versa

Collet pocket, collet and nut – the collet is inserted into the collet pocket and subsequently secured by a collet nut.


Each part of the tool holder assembly needs to be maintained separately

1.    Check for mouth wear on the spindle 

  • If the spindle is worn the tool holder cannot yield accurate results
  • T.I.R. (Total Indicator Runout) is the measurement of axial deflection on the cutting tool in the tool holder assembly

2.    Check for taper wear/ fretting

  • Check for signs of wear and tear where the taper meets the spindle
  • If any imperfections are found do not use
  • Fretting can occur as a result of the metal spindle and taper rubbing against each other. This occurs due to imperfect mating between tool holder and spindle. This causes the tool holder to vibrate and become unable to produce accurate results.

3.    Collet damage

  • If any scoring marks are found in the I.D. (Inside Diameter) where cutting tools may have spun in the collet, causing damage.

4.    Collet nuts

  • The collet nuts balance out the collet and tool holder  to maintain accuracy
  • When this becomes loose the entire assembly will lose accuracy
  • Ensure that the collet nut is tightened correctly. Tightening too loose will cause a loss of rigidity, however over tightening will wear away the threads


Click Here to be taken to the CNCRouterStore, where you can shop for all your tool holder and collet needs.


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