hobber vs milling machine

hobber and milling machine both are nouns.

Word	Noun	Adjective	Verb	Adverb
hobber	Yes	No	No	No
milling machine	Yes	No	No	No

As nouns, milling machine is a hypernym of hobber; that is, milling machine is a word with a broader meaning than hobber:

hobber: a special type of milling machine used for gear cutting, cutting splines, and cutting sprockets.
milling machine: machine tool in which metal that is secured to a carriage is fed against rotating cutters that shape it

Other hypernyms of hobber include miller, machining center.

hobber (noun)	milling machine (noun)
a special type of milling machine used for gear cutting, cutting splines, and cutting sprockets.	machine tool in which metal that is secured to a carriage is fed against rotating cutters that shape it