Lathe – graduating
Graduating on the lathe is usually done to the surface of a done part held in a chuck. The process is really like slotting on a very small scale. Each line of the scale is just a very small slot. The tool needed to do this is just a cutting edge. The width of the cutting edge is the width of the line.
It is possible to make a tool that has a handle on the end of an arm. Pushing this handle pushes the cutting edge along the surface of the workpiece. It is possible to make this tool so it includes stops to limit the length of the cut. It can be useful if the stops rotate so the pattern might be one long stroke followed by four short strokes.
On snag with this is that if the cutter breaks or needs resharpening then the width might vary. When making scales with Verniers it is essential that each line is exactly the same.
A very simple way of doing this is by using a piece of an old, broken slitting saw to make the cutter.
It can be seen that part of the slitting saw has been broken off. What left was cut in half using a grinder. The corner at the top was then ground to form a cutting edge.
This was then held in a quick change tool holder by clamping it between two piece of HSS.
This is set so the cutting edge is just touching the workpiece. It is then taken to the right of the workpiece and then adjusted to give the cut. This might be about 0.1 – 0.2mm.
Each line will end with a curl of swarf that is stuck on the workpiece and has to be broken off.