Delta 22-560 portable thicknesser

[RogerS]

Really excellent information and very helpful.

I have one last question and this may seem really dumb but...what's to stop me turning the wood over on the planer and running it through again (and again) to get down to the thickness that I want?

 

[Aragorn]

No dumbies round here!
You can keep planing your stock down to thickness, but what you don't guarentee is parallel surfaces. When the planer smooths out a face, there's no reference made to the opposite face, so you would end up with a taper. Not much use for most projects!
The normal procedure is to plane one face on the planer, turn it 90° and put the newly planed face against the fence. Plane that face and you now have two straight edges at 90° to each other.
The thicknesser uses the opposing face as a reference so when you run your stock through the machine with your straight face downwards, it planes the opposing face parallel, leaving you with perfectly straight square stock.