I removed the threads/spring from inside the nut so the bit would fit further down in.

So I'm one of those people that like to repurpose just about anything that I find. I was given a working industrial grade treadmill. I tried to sell it, nobody was interested so I figured what the heck. Let's do something with it I was inspired by a gentleman on Facebook who had a post up about making a much much more complicated and expensive Tire rock tumbler.

I figured this was a pretty easy thing to do and well I haven't used it as of yet but it's been running for about 20 minutes and it hasn't come off the tracks yet! 😜 Also they're adjustable for different size tires if I want and I can increase or decrease the speed because of the treadmill which is pretty awesome. Hopefully you all like it. I hope somebody else can copy this and show me an even better version.