Technically, a bolt is a machine. (Wire rope is a machine too.)
The tighter your tolerances the more deeply you need to go into the details. For example, a hole drilled by a two-flute drill isn't round nor straight and to make it so you need to broach or bore it. You need to check how much out-of round it is and you do that with a three-point ID micrometer, since a two-flute drill makes a roughly triangular hole. Then for straighness you need a set of pin gauges...
The softer the material the less tolerances matter. This is why plastic is cheap and machine tools are expensive.
The tighter your tolerances the more deeply you need to go into the details. For example, a hole drilled by a two-flute drill isn't round nor straight and to make it so you need to broach or bore it. You need to check how much out-of round it is and you do that with a three-point ID micrometer, since a two-flute drill makes a roughly triangular hole. Then for straighness you need a set of pin gauges...
The softer the material the less tolerances matter. This is why plastic is cheap and machine tools are expensive.