Jim_in_PA said:
There is probably none among us that has not done something like this over the time we've been doing things with tools. "Stuff happens".
A corollary to this situation is that it's not a terrible idea to have a spare for the tooling sizes you use the most...even more so if one is a commercial user doing work for others for money.
I have never hit a screw with mine, but I have hit a 23ga pin. It made a bit of a crunchy noise and went on about cutting. I took it apart and nothing seemed amiss. It cut the same, as far as effort to plunge, and was in service for quite a while after that. This was on a 6mm cutter, which is the size I use most.
I do have access to a service who will sharpen them and I have had it done a few times, but there is an issue with doing that. As it is sharpened, it gets shorter. This is a double-whammy. The depth of plunge doesn't have the same clearance. This is ok with one sharpening, but too close for more than that. The other problem is that the shorter bit makes a narrower mortise. This can make for a very tight fit of the Dominos.
After that, I quit doing more than a single resharpening. I have toyed with the idea of putting a small diameter washer (like one for an Allen head screw) behind the cutter, to push it back out. But I don't think it's worth the risk, that little registration point of the mounting stud is pretty short.
I always have at least one spare for my saw blades and most of the router bit profiles or at least an alternative method/tool to compensate. I have a new and a re-grind plus the one in the machine for the 6mm Domino cutter, plus on spare each for the 8mm and 10mm. I just don't use the tiny ones very often, still have more than half of the original bag of 4mm Dominos that came in the assortment set. But again, this is in a commercial environment, so time matters.
The shop's standard practice is to have at least 3 of everything for each of the machines. One being used, one as a back-up, and one potentially at the sharpener.