I had a machine shop pitch this idea to me. They had such a device and asked if they could use it when making some of our parts. I said sure, what's the harm,

I had a machine shop pitch this idea to me. They had such a device and asked if they could use it when making some of our parts. I said sure, what's the harm, thinking it couldn't possibly be effective for stress relief. It sounded like they had been sold some snake oil. Thanks for the link.