噛み合う

第１歯車と第2歯車が噛み合う。

ChatGPT:

The phrase "第１歯車と第２歯車が噛み合う。" can be translated as:

"The first gear meshes with the second gear."

Alternative phrasing:

• "The first and second gears mesh with each other."

• "The first gear engages with the second gear." (slightly more descriptive)

All are correct—choice depends on your preferred tone or document type (e.g., technical manual vs. patent).