Why? Because, while using one, I got carried away with the speed, & I broke a nail for the fourth time (& I never use fake nails). Let me ask you, am I the first person whose cause of broken nail is overly fast use of Nunchaku? The first nail got accidentally kicked by dad, the second was from my second grand mall seizure which happened when I fell down in the bathroom & kicked a hole in the wall (which also put some scars on my foot, & one of them is still there), the third was from my mini-seizure taking place in my right-hand thumb, it kept whacking the computer desk in my mom & dad's room until part of it chipped off. The fourth time was today. So, if I'm in any martial arts movies when I grow up, I just hope I don't have to use nunchaku.

Okay, as someone with a black belt third degree in Tae Kwon Do and with experience using these, you SHOULD NOT be using them with no training. If you're getting carried away and breaking your nails with them, please take a class instead. If there are any Tae Kwon Do (maybe karate, idk what they do though, so I'm not sure) places around you, they might offer classes. 

I had training. I quit my class, so, now it's too late, because they closed, & became re-invented as, tell me if you've heard of this, "Fifth Avenue Mall".

I'd suggest taking up a new class. They aren't something you can get carried away with, because they are weapons and if you can hurt yourself, you've got the potential to accidentally hurt others.