[jw2170]

Wow...That is a monster cutter....
When you say, "three inch ply" what dimension is that?

BTW, welcome to the forum.

 

[jw2170]

I’m sorry but I don’t think it’s a good idea to insert anything into the collet. These things are dangerous enough without adding’ foreign objects’ into the space. Do as I do and use a black marker to mark your router bit at the manufacturer mark shown on the bit. This should be enough without additional spacers etc.

I note that the new bits sold in UK have a K mark on the side of the shaft which indicates how far to insert into the collett