Two boats ago we had a locking handle that would not lock into our winches. All the dimensions checked out except the little square goodie that rotates to lock/unlock was welded to the end of the shaft from the thumb release. The round weld bead was a bit high and was hitting a set-screw that held the winch drum on. The 8-flute shaft would not go far engough into the socket to allow the lock to close. A quick pass over a grinder to take about 0.0somthing off the weld bead and everything worked OK. I do not remember the make of the handle. The winches were Barlow.