Early in 2022, at work, we had a student throw a part out of a manual lathe because of difficulty with the lathe chuck. It’s an ongoing problem with new users really wanting to leave the lathe chuck key in the lathe chuck, and standardizing lathe safety training along with getting students to retain that training is a thorny problem.
So I thought I would try an engineering control, or implementing a safety interlock that would not allow the lathe spindle to be started while a chuck key is in the chuck. I had used a lathe with an interlock of this style and I thought it was a pretty slick solution. I measured the headstock and drew up some parts. Conveniently, the wiring for the emergency stop was just under a dust cover easily accessible to the front of the lathe. I drilled a hole there and placed a limit switch operated by the interlock. Here’s the first version. ( CAD Link )
This worked well for the use case I designed for – lathe with a chuck on it – but not perfectly for the lathes set up with collets.
Visibility wasn’t great because the collets don’t stick out as far as a whole three jaw chuck.
I didn’t think this was a problem, and my coworkers didn’t notice it, so it created a situation where the engineering controls made the user experience worse. I ended up with a version with a honeycomb of holes that stuck out from the headstock just enough to prevent the chuck key from being inserted. I’m pretty pleased with it. ( CAD Link )
Paul Carson Designs 