Set turning tool - that's how it works

Dreher is not for nothing his own profession. There are a lot of things here that you have to keep in mind and execute correctly to make the result satisfactory. One of these things is the correct setting of a turning tool. Read more about this in this post.

Important parts of the turning tool

A turning tool is clamped in the lathe and does its job there - turning parts. Depending on the type of workpiece and the task at hand, different types of bits are used.

A chisel can also be made of different materials, usually high speed steels or specially hardened materials are used. This is irrelevant for the correct alignment of the turning tool.

Positioning a turning tool

A turning tool can stand in different positions to the workpiece:

  • on middle
  • about middle or
  • under middle

Turning tool on center

Middle means that the bit only touches the workpiece exactly at its center with its tip. Here is an optimal rake angle and an optimal clearance angle is given. The height to the workpiece is just right in this case. If necessary, you can change the height of the chisel still slightly with the height adjustment or by means of washers, so that a position on the center and an optimal altitude are guaranteed.

Turning tool about center

At a position above the center of the workpiece not only the tip, but also a part of the outer surface of the bit abuts the workpiece.

Here, the rake angle is too large, at the same time the clearance angle of the bit is too small. The chisel presses in this case and only very few shavings are taken off. At the free surface of the chisel, the friction is too large, and the workpiece is thus also still processed unclean.

Turning tool under middle

If the turning tool is below the center of the workpiece, the rake angle is greater and the clearance angle smaller. Sometimes that's what you want, like when you want to do roughing. For the chisel that means higher wear.

Tips & Tricks

When "roughing" only deviations from the center are allowed, which amount to about 1/40 of the workpiece diameter. Larger deviations from the center would be extremely damaging to the workpiece and chisel. If you are unsure about turning, consult a specialist.

Video Board: 150 - Bowl Turning Tools & Techniques w/ David Marks