This is a combination heatsink and purge fitting for our 68 and 73 mm threaded bottom bracket shells; it 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.
Note: if you already own our heatsink FT5007 or FT5008, you only need to buy the bronze center, FT5012, and draw bolt, FT5022; the rest of the pieces in the assembly are interchangeable.
The center is made from C-630 bronze which is 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 C-630 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.
Item sold as an 8 piece assembly.
Directions for Use
- After the frame has been tacked, remove from the fixture.
- Insert the bronze expanding sleeve into the bottom bracket shell. The sleeve must be compressed slightly to get it in the shell.
- Place both cones in the sleeve.
- Insert bronze draw bolt through one cone and thread it into the cone on the opposite side.
- Using the 8 mm internal hexagon in the bolt, tighten the bolt which will expand the sleeve.
- Install both washers with the mating nuts.
- Introduce Argon 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.