8 December 2016
8 December 2016,

Many CNC machinists got their start in a school or home hobby shop where they learned to screw collet chucks into a knee mill.  Collet holding is simple; that’s why you start with it.  It provides excellent symmetry in tool holding that’s why you stay with it.  The natural balance you get with collets reduces vibration.  That makes collets the perfect tool holder for high speed milling and a collet wrench the perfect tool for your collets.

The Collet Advantage

Collets are nothing more than a set of concentric wedges that apply force to the tool shank to hold it is place. The more you apply force to the collet, the greater the force multiplication clamping the tool.  Engineering.com finds that the run out runout characteristics of collet clamping are 10 times better than side locking tool holders.

The centrifugal force that goes into play as the tool and tool holder spins gets higher the faster you mill.  That means if the mass of the tool/tool holder is not balanced around the spin axis the faster you spin the more it you become out of balance.  That’s because any motion on a curved path represents an accelerated motion and requires a force directed at the center of the path. This force is centripetal force. In nerd words:

Centripetal force = mv2/r

m = the offset center of mass from the spin axis

v = rotational speed

r = radius of the toolholder/tool assembly

In reality, all it takes is a set screw to be slightly off to get unacceptable vibration at high speeds.  That’s why high speed machining demands the symmetry you get with collet tool holding.

The Torque Wrench and the Collet Wrench

If the collect is the perfect tool holder for machining at high speeds or feeds, then the collet wrench is the perfect tool for tightening collets.

Do you know the perfect torque?  Techniks has developed a handy torque chart.  Bookmark it for easy reference.  A quick check and you will see you need a torque wrench to properly tighten.  In addition, for best performance make sure your collet is clean.  The smallest bit of a chip on the inside of the collet or a spot of cutting fluid can keep your collet from holding as it should.

collet wrench

Make sure you use the perfect collet wrench.  5C or R8 collets can be removed with ease from the nosepiece of your mill when you use a collet wrench.

The Sierra American Multi-Systems collet wrench is made of high impact plastic molded for long life.  The large, tapered handle makes it easy to hold and easy to use.  The bright fluorescent orange color makes it easy to find.

Every tool, tray, and tool holder made by Sierra American is made right here in the U.S.A.  When you pick Sierra American, you are not only getting a great product you are supporting American manufacturing.  So, always ask for Sierra American by name.

If you are machining at high speeds, make sure you use a good collet, torque it properly, and always use a collet wrench from Sierra American Multi-Systems to remove your collets from the nose of your mill.


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