This thickness gauge performs the same function as calipers. I made it in 1982 to measure the wall thickness of the first bowl I ever made. I was totally ignorant about woodturning at the time and I made the bowl with nothing but scrapers made from old files. I still have the bowl.
The gauge is the first piece of turning equipment I ever owned. It is very useful and I use it frequently.
This is another gizmo which is very easy to make. Probably, the most difficult thing is finding a suitable piece of plastic tube to suit the available dowel.
Such a gauge can be made any size to suit the user and the wire can be bent into any suitable shape. To give an idea of size: in the one shown above I used 1/4 in. dowel 7 ins. long. I joined the wire to the tube with epoxy resin.
Before the gauge can be used the dowel must be pushed up the tube so that it is in contact with the wire; a pencil mark is then made on the dowel at the outer end of the tube. The distance between the end of the tube and the mark on the dowel then indicates the thickness being measured.