"Is a Machine Screw a Bolt?
The exact difference between machine screws and bolts is not always clear, particularly as their appearance is similar. However, machine screws are typically smaller than bolts, although a more precise distinction is the way that they are tightened in a tapped hole.
Bolts tend to be driven home and then tightened fully by turning the nut on the rear side of the fastening. With machine screws, the majority of tightening force (torque) is applied to the head of the screw itself when driving it into a tapped hole.
A further dissimilarity for bolts vs machine screws is that while all machine screws can be effectively used as a type of bolt, the same is not necessarily true in reverse. In other words, not all bolts can perform the full range of functions as a machine screw."
I don't know what an example of the last paragraph is, but I think what you're talking about is a machine screw. But I think most people wouldn't know what you were talking about referring to them as machine screws :)