Dawn,
I believe that it is very appropriate and proper to measure the supplier's performance against what he says he will to. In your example, if he said he was going to deliver the tool the next day, it should be counted as late if it is not there.
However, it is beneficial if you, in your measurement, also indicate that the supplier was not given his normal leadtime, if that is the case. While missing a promised delivery is never a good thing, it is more understandable when a supplier is a couple days late when he was only given a small percentage of his normal leadtime.
In a previous life, when showing a suppliers delivery performance for the month, I broke it down by On Time and Late (with degrees of lateness), but also showed how many short lead time orders were On Time and Late. It certainly helped with supplier relations and with management's perceptions of suppliers performance when the periodic summary shows that level of information.
------------------
Tom Goetzinger