This countersink drill bit is used to install new inserts into a snowboard.
First, a 5/16 pilot hole is drilled through the snowboard. Then, the
bit drills an optimal countersink into the base of the snowboard to
accommodate aftermarket inserts that have a rounded flange. After
the insert is attached with epoxy, a plastic disk the size of the
outer countersink diameter (20 mm) is glued to the back of the insert,
then a disk of P-tex is glued to the plastic and is shaved down to
be flush with the rest of the base.