A blade for mounting to a scraped surface heat exchanger drive shaft by pivotal connection with a mounting pin has a blade body having a first side and a second side, and a scraper edge and a hinge edge. At least one mounting hole extends through the blade body generally proximate at the hinge edge. An L-shaped locking track protrudes into the first set of the blade, having an entry track extending from the hinge edge and an intermediate track extending from the entry track to the mounting hole. An L-shaped locking track also protruding into the second side of the blade, has an entry track extending from the hinge edge of the blade and an intermediate track extending from the entry track to and past the mounting hole.