A rotary retort furnace wherein the retort is supported for rotation at only one end outside of the heated furnace shell such that the retort is cantilevered into the shell. The rotary retort has a charging door mechanism that cooperates with a skip hoist loading mechanism to provide charges of the parts to be heat treated that are of a uniform size and are introduced into the retort so as to minimize the loss of any controlled atmosphere. The skip hoist loading mechanism has a vibrating feed hopper that dispenses a weight controlled charge into a skip hoist bucket which, after receiving the predetermined charge of parts, is held in a ready position until such time as a cam mechanism controlling the opening and closing of a door on the charge end of the retort causes the door to open and the skip bucket to be moved to a position wherein the parts are dumped into the retort for heat treating. The internal auger flight for the retort is made by forming a number of toroids from a resilient material, radially cutting each of the toroids and deforming them to form individual flights, and connecting one of the split edges resulting from the cutting to the opposite edge of an adjacent flight such that an axially compressed helical subassembly is obtained. The helical subassembly is then screwed onto a shaft having a number of guide pins axially on the shaft at predetermined spacings thereby both axially extending and radially compressing the helical subassembly. The shaft and the helical subassembly are inserted into a retort shell and one free end of the subassembly is welded to one end of the retort. The shaft is then unscrewed from the subassembly while at the same time being forced axially into the retort such that the edges of the helical subassembly fit tightly against the inside of the retort. After the shaft has been removed, the remaining end of the helical subassembly is welded to the end of the retort.
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