Laser Depth Finder for the Lathe

by Dave Smith

I was turning a natural edge bowl and needed to determine the inside depth of the bowl before parting it off. I have a shop made depth finder that is OK when the bowl rim is uniform. But because the uneven rim of a natural edge bowl requires a different measuring device, I commenced the "noodle dance" to come up with an alternative method for measuring the inside depth of a bowl and transferring that depth to the out side of a bowl. I was considering a mechanical arrangement when I saw the laser light I purchased with the Laminate Pro software program. It was then that I had, what Tom Peters calls, "A blinding flash of the obvious." It only took a couple of minutes to set up the whole system.

A drill chuck is placed into the tail stock with a 1/4" socket extension of sufficient length to reach the bottom of the vessel being measured. Any suitable rod that fits into the drill chuck will work. I chose the 1/4" extension because I have a selection on hand and the male end is not larger than the shaft so it will seat properly in the chuck. The laser light's magnetic base is attached to the tail stock. Next align the laser beam with the end of the extension.

Note that my camera took the red out of the laser light beam which appears as a white dot in the photo.

Move the tail stock until the extension contacts the bottom of the bowl. The laser light will indicate the depth of hollowing which can be conveniently marked on the outside. This method is more accurate than sighting along dowels and trying to mark the bottom of a vessel.

I purchased the laser light from Wood Turner Pro for $50, and used it because I had it on hand. The magnetic base and goose neck are very convenient for mounting and aligning when needed. A similar combination is probably available elsewhere.