Replacing a mortise lockset with a cylinder doorknob lock

This was a sufficient pain in the butt I figured someone else might benefit from the invective overview.

A mortise lockset is one of those old style locks that's got a rectangular case that fits into a hollowed out pocket inside the door. They generally open with a bit key (see also, skeleton key) and tend to be quite old and cranky.

The first advice you will see, if you look up how to replace or convert a mortise lockset is "get a newer mortise lockset". This is because it's a royal pain to convert a door for a cylinder doorknob lock. As long as you know what you need ahead of time, though, it's mostly just time consuming.

( It's all about the details )

I hope this helps someone, because figuring out all of this on the fly was not a recipe for a relaxing and peaceable weekend.