What's the best type of knife [and/or method] for cutting raw bread dough? Is a special dough blade necessary, or will any blade suffice?
I work in a fine dining restaurant, and the standard implement is a bench scraper AKA a dough knife AKA a bench knife. It's basically a stiff, 6" wide sheet of stiff metal with a handle, and can pressed or rocked down on the counter to cut dough into portions. It can also be used to move shaped bread or rolls, cut pastry, fold sticky doughs, and scrape off the counter for cleanup. They're not really knife-sharp per se, but the metal is narrow enough to cut dough well, and a knife would go dull against the hard surface anyway. The best models have measurements engraved into them, so you can consistently size your products, and will stand vertically on the handle (for icing cakes).
Now, for SLASHING risen breads before baking, the correct tool is something called a lame, which is basically a razor with a handle. Or, you can just use your really sharp chef knife (your chef knife IS razor-sharp, right?) and spritz it with pan spray to keep the dough from sticking.
A knife large enough to not require a slicing motion. You want chopping or even better rolling motion. Any sharp knife will be ok but I have some preferences:
In a pinch I use my plastic dough scraper. A metal scraper with a flat blade is adequate, for example this one.
Pizza cutters are ok but if there is too much dough then they get bogged down.
My all time favorite tool for this - and I have more than one just for this purpose - is an ulu. This is a curved knife used traditionally by native Alaskans. Mine is big and rolls through a lot of dough easily.
from this one on Amazon
Assuming it is just yeast dough and you aren't trying to preserve some lift characteristic, you don't want a knife. You should have a bench scraper as your go-to tool for handling dough, it is not sharp, it is wide and flat so it does an excellent job of scraping dough up when it sticks to the bread board, and it is completely capable of cutting through dough if you are subdividing.
It is also plenty handy for actual bench scraping... i.e. getting remnants of old dough off your cutting/bread board/counter.
My mother used to roll a sheet of dough into a tube for cinnamon rolls, then cut the individual rolls by wrapping a piece of string around the tube and pulling both ends until it cut through.
For most kinds of dough any blade will do, but you may want to sprinkle some flour on the knife if the dough is sticky (especially if the dough already contains flour; for non-flour ones, it may be a problem)
I've never seen a special knife, but I often use a long, thin, smooth edged (not serrated) blade. Cuts cleanly. Doesn't stick. Doesn't crunch the dough.
The only knife I would avoid would be a serrated blade because of how the teeth "hook" material to tear.