Get a high end bulkhead from aquaticeco.com, say 1/2'', cut a hole w a holesaw for the od of the threads, and then a bushing to reduce to your 1/4'' npt. The high end bulkheads are worth it imo. Put the flange part of the bulkhead, where you want the gasket, on the inside. That way, no wort gets into the insulation in the cooler walls. This is also a robust way to add a drain for the wort.