Well, actually… it’s ground into a powder, rather than the byproduct of sawing. I don’t think it counts.

What would you do if he wasn’t your dad? You mentioned you took full blame, almost as if you felt like you were covering for him, but I think even if it wasn’t your dad, you’re responsible for anyone you bring in, and the work they do, so taking the blame should be universal. And going forward, I’d expect a similar, universal approach. You could choose to not mention it but also not employ that person any more, mention it before the next job and ask them to be extra careful, change procedures to guarantee it doesn’t happen again…

I don’t think him being your dad should necessarily afford him special treatment.