http://na.finalfantasyxiv.com/jobguide/machinist/

Unless I missed something... we will only start really benefitting from the 50-99 heat gauge once we aquire the level 64 trait turning our 1-2-3 into Heated versions? Otherwise its just the Cooldown move at 62 getting a damage buff between 50-99? That the obvious overheatting giving us an overall damage increase for 10 secs of course.