Posthole Digger used post hole auger bits?

[skspurling]

I borrowed my dad's F8 digger, and was wanting to dig some holes for tree planting. I was wondering what people do with their old augers. Can you buy them for light use or to "re-flight" them? I'd like to get my hands on an old bit I could widen to make some big shallow holes. Just curious what others have seen.