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Paragon Heatsink and Purge Fitting for Threaded Bottom Bracket Shell
Item #PG-FT5002: This is a combination heatsink and purge fitting for all of our threaded bottom bracket shells. This assembly will work with both 68 and 73 mm shells, and is specifically sized to fit our shells with a 1.390" center relief. All metal to metal interfaces are bronze to stainless steel. These two metals have a very low coefficient of friction with each other, making sticking, binding or galling very unlikely. Although it introduces argon into the frame and absorbs heat from the weld to reduce distortion, it will not completely eliminate it. Results will vary based on tubing diameters, wall thicknesses, and personal welding styles. In our shop tests, we were able to install a threaded bottom bracket assembly with no post-weld machining.
The center is made from 510 bronze which is a spring alloy and a very good heat conductor. The center expands with two cones, made from 303 stainless steel, to fit with minimal clearance on the interior diameter of the bottom bracket shell. One cone butts against the draw bolt and the other is threaded female 1/4" NPT for the argon connection. The draw bolt is 954 bronze, and is drilled to accept argon from the threaded cone. The draw bolt has an internal hexagon to accept both a 5/16" and 8 mm Allen wrench. Two 1 5/8" diameter stainless steel washers are supplied to plug both ends of the bottom bracket shell. They are pulled together with two M20 x 1.5 nuts.
Directions for Use
After the frame has been tacked in a fixture, it can be removed from the fixture. The bronze expanding sleeve is then inserted into the bottom bracket shell. The sleeve must be compressed slightly to get it in the shell. Now both cones can be placed in the sleeve. The bronze draw bolt is inserted through one cone and threaded into the cone on the opposite side. Using the 8 mm internal hexagon in the bolt, the bolt can be tightened, expanding the sleeve. Now both washers can be installed with the mating nuts. Argon can be introduced through the connector (not included). The connector fits inside a standard 1/4" internal pipe thread in the cone. To remove the heatsink, reverse the above procedure.
Item sold individually.