For long shank bits, you can place the washer so that it won’t bottom out in the spindle.
For bits with larger diameter cutting profiles, like the Vee bit pictured, it prevents you from tightening the collet down on the radius part where the shank meets the cutterhead.
With the washer pressed up against the bottom of the collet nut, it helps keep the insides of the spindle and collet cleaner.
About the only issue I have with them is that when on the bit, the bit no longer fits into the narrow plastic boxes it came in. Not a problem if you store the bits in a tray, or just remove them before you put the bits away.
I use small grommets for my routers except I install them inside the shaft until they bottom out. This ensure I don’t run the bit into the shaft when tightening them up if I need the clearance and have to slide the bit all the way into the shaft.
I really appreciate the depth setting rings that come on the bits from precisebits.
You can buy them to put on your own bits but you would have to rig up something to apply them. Maybe as a community we could come up with something reasonable
Note: Depth rings for 1/4 in. shank bits are not compatible with ER11 spindles or Dewalt 611 and Porter-Cable 450 routers without the use of a positioning spacer. The rings interfere with the operation of the collet nut during tool removal.
I have no issues with the thinner rubber washers on my ¼" shank bits on my C3D ER11 collet router.
