The Machine that Spins

I once heard about a machine that spins stuff – I don't know what, exactly. For the purposes of this story, just accept that it's a spinning machine with an open top and it's used to do something dangerous. Two people are on the machine at all times, even though you only need one to work it. You see, the machine spins so quickly that it almost looks like it's not spinning at all. The interior centrifuge is so fast and so powerful that if you stare at it long enough – which you have to do if you're going to use it properly – your brain forgets that it's moving because your eyes are telling it that it's not moving and so your hand naturally reaches into the machine and that's how you can lose your hand, up to the elbow, they say...