donut machine vs doughnut machine

donut machine and doughnut machine both are nouns.

Word	Noun	Adjective	Verb	Adverb
donut machine	Yes	No	No	No
doughnut machine	Yes	No	No	No

As nouns, donut machine and doughnut machine are synonyms defined as:

donut machine and doughnut machine: a machine used to fry large quantities of doughnuts at once.

Other synonyms of donut machine include donut fryer, doughnut fryer.

donut machine (noun)	doughnut machine (noun)
a machine used to fry large quantities of doughnuts at once.	a machine used to fry large quantities of doughnuts at once.