When I use a jam chuck to turn the tenons off the bottom of bowls I like to use a silicone pot holder to protect the inside of bowls. Not only does it protect and give great cushion to the inside of the bowl, but it also provides great power transfer from the lathe. I start by Installing the jam chuck, in this case I'm using a screw drive to hold it on. Next I place the hot pad over the jam chuck, then put the bowl on top of that. I slide the tailstock up to the bottom of the bowl, align it on the center mark, crank up the tailstock to apply pressure, and secure everything down. After that you're ready to turn! I hope this tip helps, please check out the video on my youtube channel, and if you aren't able to find those silicone pot holders in a store near you here.s a link to them on amazon.