Bowl depth gauge

Ever made a lampshade out of a bowl?  I’ll never admit to it, but I’ve heard of people hollowing right through the bottom of a bowl 😉

I recently turned a bowl and the bottom was a lot thinner than I liked and getting dangerously close to becoming a lampshade.  So I decided to make myself a better bowl depth gauge.  Something more accurate than my current method of holding my gouge at the center of the bowl, eyeballing along the rim of the bowl and then bringing the gouge up and out of the bowl to eyeball how deep I was with my hollowing.  I wanted something that would be accurate, but would still be quick and easy to use.

A visit to the plumbing section of Home Depot and I returned with a couple two foot sections of 3/4″ PVC, two tee sections, a 90 degree elbow and a cap.  The wooden morse taper I turned and the rifle laser was purchased off Ebay.

I cut one of the PVC pipes in half and then cut an 8″ section off the other.   (The length of the 8″ section was determined by the swing of my lathe, half of 16″.  I cut the other pieces to 12″ as with the current tools that I have I’m unlikely to be turning a hollow form any deeper than that.)

Depending on the laser sight you get some adaptions may be needed to one of the PVC tee pieces. In my case the diameter of my laser sight was slightly greater than the internal diameter of the tee piece.

I mounted the tee piece in the pin jaws of my chuck using a 60 degree live center to help mount it true.

Then, with the lathe speed slowed down, I drilled it out with a Forstner bit that matched the diameter of the laser.

A nice snug fit.

I turned a tenon on the wooden morse taper that matched the internal diameter of the PVC pipe and then I pieced all the parts together.

Here is the depth gauge mounted on the lathe.  The wooden morse taper is inserted in the tail stock.  It is not necessary to jam it into the tail stock.

Side note: With a self ejecting tail stock it is not considered a good idea to use a wooden morse taper.  Click here to read a discussion on this subject.

So, throwing caution to the winds, I mount my bowl depth gauge in the tail stock.   Once everything is adjusted and the laser is shining on the tip of the cap, a couple of drops of CA glue can be applied to each of the PVC joints.  Don’t glue the laser into the tee piece though, at some point you will need to take it out and change the batteries 🙂  The laser sight I got has a switch to turn the laser on and off,  a lot more convenient than the lasers you get from stationary stores which require you to constantly depress a button for the laser to be visible.

I’m still trying to get a good shot of the laser on the outside of the bowl.  When I do I’ll update this post with a picture of the depth gauge in action.