I bought a cheap version of this machine, because all decent ones had costs of hundreds of dollars of transport to my region. The machine seems to be made of solid parts, but is really badly assembled. I hope to reassemble it into a working state. This is how it should look like:
And it is the photo of the worst part of what I bought. My question is about the brass (?) nut:
What is the role of the nut? Why it has something which looks like a small ball inside? Should it be put in the position, in which it is in every other photo of this machine?