The steps necessary to hold the accessory in place on the 4200 are faster to actuate than unthreading the collet nut or chuck, however it's still really important to execute the steps completely. First make sure you are inserting a shank size that is a match for the collet you have in the 4200. In other words, if you've never changed the collet on your 4200, double check the shank size on your accessory – make sure it's a 1/8 shank. Then, pull the blue EZ change levers back (and keep them back) so all of the pressure is off the collet and insert the shank of the accessory as deeply into the tool as you can. Once fully seated, pull the EZ Change levers FORWARD toward the nose of the tool as far as you can. This will secure the accessory. The accessory should not slip during use. In the event you experience anything of that nature during use, you can try the following: Remove the accessory and remove the collet. Make sure there is nothing in the collet that is causing the accessory to stay slip (like debris or the broken end of a different accessory). Blow out the nose of the tool, or the EZ Chuck portion and then re-insert the collet, then the accessory and tighten completely. Two things to keep in mind: with extended use, the collet will wear and may require replacement. Also, If you are experiencing accessory movement during use after doing these simple trouble shooting steps, please contact us so we can provide service for your tool. The accessory should always be secure during operation.