My mom sometimes makes her own peanut butter with a staff mixer. She has to use oil or syrup to get it to stick together, and even then it usually turns out pretty stiff and unspreadable. I've tried it myself with my blender and got fairly similar results.
Recently my mom bought some nothing-but-peanuts-in-it peanut butter from the store. (Apparently it was the only kind they had without palm oil.) Far from being stiff and unspreadable, it was basically swimming in oil. So my mom thought that by making some of our home-made peanut butter and mixing it with the store-bought stuff we would arrive at a happy medium. Which worked just fine.
This got me thinking, how could the factory and us get such different results from the same product? Maybe by grinding the peanuts up more finely the factory machines release more oil from the structure of the peanut. A while back I had looked up how to make cashew butter, and the instructions I found said you didn't have to add extra oil. That had got me thinking that by chopping the nuts up finely on an old-fashioned cutting board first I might be able to make good spreadable nut butter my blender. The whole peanut butter thing gave me the push to actually try it out.
Now my blender is not "state of the art" in any sense of the word. It says "do not use for over one minute" on the side in big letters. I'm pretty sure that doesn't mean "per day", but I have no idea how long I am supposed to let the engine cool (or however that works) between blending sessions. Anyway, it worked fine for the first batch of peanut butter, but halfway through the second batch the blender's blades wouldn't turn. It would make some noise, so I was pretty sure the engine wasn't burned out. My dad and I took the thing apart and it turned out two screws had gotten loose and got stuck between the casing and the outer thing that turns the blades. The engine itself was fine. So we put the screws back where they're supposed to go, put my blender back together and now it works again. And by "works" I mean "makes smoothies, which no-one in my family eats, so let's take this thing to the 2Switch and get a food processor or something". Which we haven't got around to doing yet.