One thing I noticed in the original post was that in the first scenario it was never brought up that he didn't have a hammer. If that had been brought up I would have immediately offered for him to borrow the hammer, and if he was a nice guy about it and offered to return it promptly and whatnot, I'd just tell him to keep it.
If he fails to bring up that he doesn't have a hammer, then I would still let him borrow.
Asking for someone elses perfectly good and frequently used property is a nono on his part
(but if the hammer was 10 years old and laying in the corner of the backyard forgotten about, yea, he could ask for it just fine.)

If he fails to bring up that he doesn't have a hammer, then I would still let him borrow.
Asking for someone elses perfectly good and frequently used property is a nono on his part
(but if the hammer was 10 years old and laying in the corner of the backyard forgotten about, yea, he could ask for it just fine.)