This is just a short post on how to remove the core from an American A20 padlock. Was sent this lock without a key and a core with keys to make a swap.
The AC20 lock looks like this:

And is a dual-sided wafer lock.

It was already unlocked when it arrived, but it is easier to get the core out with the plug turned to the unlock position as it takes spring tension off the core. So picked it.

Now if you look into the shackle hole, you will see… nothing!


But that is OK, because you are not supposed to see anything yet. Now get a piece of soft wood, a rawhide mallot, or a plastic mallot… anything that will not mar the lock when the lock is rapped a couple times against it. Then hold the padlock by the shackle with the open shackle hole of the lock body facing downwards, and rap it a couple times on the mallot with the side of the lock.

Now look in the shackle hole…

There is a pin at the bottom of the lock body starting to move into the hole. (Moving upwards in the picture. Still not moved all the way yet, so rap it a couple more times.

And a little more:

Finally! When the pin has moved to the far side of the hole, you are done with knocking the lock into submission. For now.

Now use a hook to catch the inside of the plug and give it a tug. The core will come out.

If you look at the core with the keys on the right, you can see the groove that the pin slides into to lock the core in the lock body. On the left, the groove is facing down. This grove limits plug rotation past the unlock position, or past the key removal point when locked. (This lock is not key retaining, but it only opens when turned clockwise.)
Now look in the lock body where the core went. Near the outermost point on the side facing the shackle hole, you will see a hole.

That is where the pin is located. If you push the pin out of the shackle hole, it will show itself and how it holds in the core…

If you use tweezers, you could pull out the pin if you wanted. Just swapping cores on this lock, so it gets pushed back towards the shackle hole. Insert the new core using the key, then rap the lock on the mallot again to move the pin back in, retaining the core in the lock again.
Don’t forget to try your key BEFORE locking the lock again to be sure the cam is lined up correctly. If it is, then you are done. As is this write-up. Hope it helps someone out.

Gordon