Just some additional info:
The hole is a tapered hole and must be located correctly in the axle to 'lock' the kingpin in the axle. I believe the taper is 7 degrees. Check the locking pin for the correct taper. The large end of the taper is at the front of the axle. The long nut on the locking pin acts as a spindle stop as well as tightening the lock pin in the axle.