Collet maintenance

The collet is often taken advantage of by some CNC owners. By this I mean that they are ignored quite often and this can present problems down the road for the operator. Some issues which may arise are tool breakage, poor cut quality and even worse, damage to your expensive spindle.


Collets are made of spring steel and the more often a tool change is made the more the collet expands leaving the tool to slip and shift around.


The most important portion of the collet is the mouth, which is located at the bottom end from where the tool extends. This area is important because all the lateral pressure taken by the tool must be evenly distributed on all sections of the collet for it to be true or concentric. Not colleting the tool in perfect alignment results in tool breakage.


I made of a short set of rules which can help you avoid any problems, acheive good cuts and actually extend the life of your router bits.

Rules of Proper Colleting

1. Always change and throw away your collets after machining for 400-500 hours. This is 3 months time in a normal two-shift operation.

2. You can tell if you require replacement if there are any markings or abrasions on the inside of the collet or on the tool itself. This indicates slippage of the router bit inside the collet.

3. When inserting the bit into the collet do not let the flute fadeout portion of the tool extend into the collet. Insert the shank of the bit 80% into the collet and you will have perfect concentricity.

4. Each time you make a tool change, clean the inside of the collet and the tool itself. Do not use a petroleum based lubricant as it will only act as a magnet for all the dirt and dust by the residue it leaves behind.

Rigidity and concentricity are the key elements in any routing application. The simple process of properly colleting router tools, maintaining collets, and replacing them at regular intervals will safeguard the productivity of the operation and insure that the finish of parts is not jeopardized.