How fast would you spin a 14" diameter bowl?
In a discussion on the World of Woodturners site, Richard Raffan posted a picture of a 14" red gum bowl that detonated while he was turning it. It happened while he had stepped away from the lathe, so he was well out of the line of fire when it blew. This was wood that was riddled with voids (gum pockets) and is known for being tricky to keep in one piece.
Later in the thread Richard mentioned he "wasn't spinning the wood that fast", somewhere around 1000 rpm for the 14" piece. Another poster mentioned that there are about 200 Gs trying to rip the rim off a 14" bowl spinning at 1000 rpm. Yet another poster said that reducing the speed to 700 rpm would cut the G forces in half. Reducing to 500 rpm would be one fourth of the G forces as 1000 rpm. (Smaller diameter pieces would have lower numbers and larger pieces would be higher.)
I just thought those were interesting (and eye-opening) numbers. Something to think about the next time you're cranking up the speed on the lathe to get a better cut. Richard has been a professional woodturner longer than I've been driving cars, so I'm sure he felt comfortable turning a piece that size at that speed. I don't think I would be.
When I started turning, I kept the speeds pretty low, because catches were all too common, and low-speed catches were less dangerous and destructive. As I've gained turning experience, I'm bumping the speeds higher and higher, since I get a better cut when the lathe is spinning faster. I've gotten very comfortable with a bowl gouge, and catches are very rare (and typically very minor) these days, so the risk of catastrophe feels lower to me than it used to. Still, 1000 rpm on a 14" piece would feel awful fast to me. (My current limit for finishing cuts on a piece that size would probably be around the low to mid 800s.) I'd probably love the cut I could get at 1000 rpm, but in the back of my mind would be this little movie running, showing how quickly an edge could break off and stick into anything in its path.
So...how fast would you spin a 14" bowl?