An electrical thermostatic switch, prior to calibration, has a flexible blade which is spring biased into contact with a thermostatic member. The end of the blade is submerged in a heat curable material. The switch is placed in an oven at a predetermined temperature level for calibration, with the result that the thermostatic element moves the flexible blade into the desired calibration position prior to curing of the heat curable material. The flexible element is thereafter held by the cured material in the desired calibration position.