Jacek Zagaja wrote:

Some older lathes doesn't have an angle scale on a toolpost.

Here's another approach that works well for me.
http://www.metalworking.com/dropbox/Deg-Scale.txt
http://www.metalworking.com/dropbox/Deg-Scale1.jpg
http://www.metalworking.com/dropbox/Deg-Scale2.jpg
http://www.metalworking.com/dropbox/Deg-Scale3.jpg

Ted