I have three Dremels and use both the collets and the chuck.  They both have specific uses and are not 100 percent interchangeable.

While the chuck is quicker to load and unload (especially with varying diameter shafts such as drill bits) , it was primarily designed for tools such as drill bits where the force is applied in line with the shaft.

It takes a little bit longer to insert a tool into a collet and lock nut, but the shaft is now gripped around it's entire circumference instead of just the three points of the chuck.  Thus you should use a collet with any bit where the force is applied laterally to the shaft and you want precision and minimal wobble.  These include bits such as routers, shapers and grinders.

BTW, I found this on the new "Getting Started" page.  I never knew that the collets were marked with rings to indicate their size.  Of course, most of the bits use 1/8 inch shafts and hence use the plain collet.

The Collet

The collet is the most precise way to hold an accessory(bit) in a high speed rotary tool. The collet is located underneath the collet nut, inserted in the end of the tool’s shaft. There are 4 different sized collets available to accommodate different accessory shank sizes from 1/8 inch down to 1/32 inch. It is essential to use the correct sized collet for each accessory. The collets are marked with corresponding shank size: no rings – 1/8 inch (480), 1 ring – 1/32 inch (483), 2 rings – 1/16 inch (482), 3 rings – 3/32 inch (481). See your owner's manual for more detailed information.

I hope that helps explain why Dremel sells both.

Gary

I use both the Dremel Chuck and wrench-free collet and lock nut extensively.  

My practice is to leave which ever is on the tool (the chuck or collet and wrench-free lock nut) on the tool for the next use. Also, the Right-angle Attachment lives on my Dremel as I find it (and the flex shaft) handy for much of the work I do.

99% of my work is with 1/8" shaft tools so either the chuck or wrench-free collet usually work ok.

Overall, I prefer the wrench-free collet and lock nut as I've NEVER had an accessory come loose with a collet. I have had accessories come loose rather frequently from the Dremel Chuck so I compensate by vigorous tightening and then, checking to see that the chuck is tight several times during my work.

My habit is to use either the 1/8th collet or the Dremel Chuck for most of my work and to use the Dremel Chuck for small shaft tools such as drill bits and smaller shaft accessories.

This system works great and my Dremel 395 has sufficient power to muster speed against the inertia of wood and metal.

Thanks to Dremel Co. for making the most versatile tool in my collection.

There is one thing that would make Dremel tools even more useable - and that is to make them REVERSIBLE, like my drill.

Blessings,

RimeBuddha

Some manufacturers offer collet inserts that make it possible to switch back and forth between different shaft sizes without removing a collet. I've also modified some 3/32" shaft accessories by sliding a sleeve of brass tubing over the shaft.  This allows me to chuck it into a 1/8" collet so I don't have to change them.

Bonnie Gibson - Arizona Gourds

http://www.arizonagourds.com