Abstract: A thermally compensated circuit breaker has a movable contact assembly (24) which mounts a movable electrical contact (24m) for movement between open and closed contacts positions with a stationary electrical contact (26). The contacts are maintained in the closed circuits position by a latching mechanism (24b, 28g) which prevents opening of the contacts through an opening contacts force provided by a spring (24e). A current carrying trip arm (40a, 44a) deflects upon sufficient I2R heating to transfer motion to the latch to separate the latch (24b) from the latch receiving catch (28g) to trip the circuit breaker. The trip arm (40a, 44a) is part of a pivotably mounted actuator assembly (40, 44) having a movable end portion spaced from the pivot disposed adjacent a motion transfer member (28c). A calibration screw (42a) is located so that the longitudinal axis is in line with a movable end portion of the actuator assembly and the motion transfer member.