Welp I royally screwed up.
You're all going to read this and think I'm an idiot, maybe I am, I guess that's what inexperience and youth gets me.
The engine is still fine luckily, doesn't involve that.
My method so far for lubrication was a small bucket of 10-40 engine oil, worked pretty good on the first cylinder, but got dirty quickly as I was just dipping it in to both clean and lubricate the stones. I did 60 passes on cyl 2 and was wondering why the stones weren't cutting like they did on no. 1, then I remembered a clip from a video where the guy cleaned off the stones in a bucket of soapy water. So I figured it wasn't cutting properly because the oil was full of grit and blocking up the stones.
Went and got a bucket of water and intended on changing the lubricating oil, spun it around a bit in the water, how do I dry it off?
Spin it reeeaallly fast in the air of course!
The thing suddenly explodes in all directions with a loud CRACK PING PEW ---- silence.
I stand there dumbstruck for probably 15 seconds and BANG on the shed roof behind me, holy jesus it must've flown high.
All I can say is I'm extremely lucky none of the bits hit me, or any of our cars that're parked nearby.
But there goes my $90 tool, and 1 cylinder is honed.