About this 3D model

I am a high school teacher, and I had made a hand spinner to teach my students how to made one by themselves.http://www.thingiverse.com/thing:2197998https://livingtechlearn.wordpress.com/2017/03/18/使用onshape繪製手陀螺/ Then I had heard some school think it is too danger.So I draw a dart version. Be careful. :) 4mm steel ball 9608ZZ1M35mm 3 ( Screws and nuts )