You need a #2X56TPI tap and a tap drill for the same. If your clip has 2 holes; drill, tap, and anchor the clip on one side with the appropriate #2X56TPI pan head screw. Line the clip up with the axis of the knife and lay out the second hole with a transfer punch. Now drill and tap the second hole. Whenever I mark 2 holes on a handle, either the spacing is off or the clip is crooked.