Often, the taper pin has been hammered into the crankshaft assembly, deforming the column in the area around the taper pin hole. With the tool head all the way down, try rolling a very fine file over the hole in the column on both sides. You should be able to see if there is some raised metal around the hole. Keep going until it's gone.
In some instances the keyway in the column gets buggered up. You can run a flat file along the two sides of the keyway to see if there is any raised metal that has to be removed. Also check the outside edges of the key way. The key in the tool head doesn't usually contact the bottom of the keyway, so you probably don't need to worry about the bottom of the keyway unless you see obvious damage.
Bruce Williams