That is not really an easy question, or at least not a common one. The machine has ~80mm of travel. That means you have ~40mm of cutting depth if you can find that long of an endmill. Not material thickness is completely separate from that number and is not constrained in any way.
If you need to cut a 40mm hole in the end of a log you can, you just need to make a table (drop table) that can accommodate your material height. The only limitation here is that 40mm.
The most common use for something like this is surfacing slabs. You make a deep table and the machine is only cutting a 1/4" or so off the surface but the slab is 4-10" thick.