Further to what Bazyle says about angle scales. Normally you'd set the table angle by reference to the existing tool angles or, possibly, a simple sheet angle reference for something special. Once you have the knack its far quicker to loosen the handle, adjust the table so the tool sits properly against the wheel and lock up again than it is to read a scale. Especially as said scale is probably covered in guiding dust, hidden under the table and, if its one of the import style linked to by Vic, not super accurate in the first place.
Generally when it comes to lathe tools sharp beats dead to book angles all the time except for special cases like screwcutting. If I had one I'd probably sort out some sort of rotating cam stop for the three or four table angles I might need.
As the name suggests its designed as a trimming tool to re-sharpen worn tools or sharpen tooling already ground to shape, either in the toolroom or purchased welded tip and brazed carbide on a shank style. Which were once readily available rough ground in a much wider range of tip shapes than can be found today. Georges' Abwood is a toolroom beast. Not shop floor.
Clive.
Edited By Clive Foster on 16/03/2019 12:17:16