Yes, RATCHETS is a Scrabble word!

Letter values in Scrabble US: R 1, A 1, T 1, C 3, H 4, E 1, T 1, S 1.

Is it a valid word?

RATCHETS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

mechanical device consisting of a toothed wheel or rack engaged with a pawl that permits it to move in only one direction

Also: rachet up, ratchet down.