Vacuum chucking- be aware!
Dear fellow woodturners:
I want to share an experience I had with vacuum chucking that was a near disaster. First of all, let me say that I have had a lot of experience with vacuum chucking. I been using vacuum on three different lathes in my shop for at least ten years with great success and very few problems.
I was just finishing up an order for three bowls and decided to use a vacuum chuck when finish turning the bottoms. As a safe practice, I routinely leave the live center against the bottom of the piece until I have removed as much waste stock as possible then start the vacuum pump and slide the tail stock away. As usual I checked the vacuum gauge first and observed -24" Hg. As soon as I removed the tail stock the piece flew off the lathe and landed about 10 feet away.
I put my finger over the inlet of the pipe that goes through the spindle and felt no vacuum or flow, but the gauge still registered -24" Hg. I pushed a long drill bit through the pipe and dislodged a mud dobber's nest and immediately attained vacuum and flow.
Amazingly, my piece wasnt damaged!
The first mistake I made is I pulled a through pipe off the shelf without checking it for blockage (I live in Florida). The second mistake I made was not turning the lathe off before removing the tail stock.
I hope some of you will benefit from my misadventure.
Don Geiger