Bottom bracket facing and thread cutting is a procedure preformed during the manufacturing of the bicycle frame. It is not uncommon for bottom bracket threads to become damaged because of improper installation, and other factors including corrosion. Chasing these threads with a specific die can repair, and redefine the threads for ease of bottom bracket installation. The facing procedure is much like head tube facing as the 2 sides of the bottom bracket shell need to be completely flat and paralell to each other. If the faces are not square it will result in prematurely damaged bottom brackets. Here at Winterborne Bicycles we have taps for both English/ISO/JIS (1.375" x 24TPI), and Italian (36mm x 24TPI) Bottom bracket shells.
*Chasing Bottom Bracket Threads and Facing are done at the same time so this price includes both procedures.