THE PRIVATE PILOT (FLYING HIS OWN AIRCRAFT) MADE A NORMAL LANDING UNDER CALM WIND CONDITIONS. ON TOUCHDOWN, THE AIRCRAFT SUDDENLY SWERVED AND THE PILOT WAS UNABLE TO REGAIN CONTROL BEFORE THE AIRCRAFT GROUND LOOPED, DAMAGING THE RIGHT WING AND COLLAPSING THE LANDING GEAR. SUBSEQUENT EXAMINATION OF THE TAILWHEEL ASSEMBLY REVEALED THE CENTERING DETENT HAD FAILED DUE TO EXCESSIVE WEAR.