This is the Tool Offset Cancel G-Code known as G49. This code is useful for clearing out the current tool offset and returning the value to zero. It is useful during Automatic Tool Change (ATC) operations when using the G43 code or when setting the Z-offset manually to the part.
Standard Format G49
The code requires no additional parameters.
The usage of the G49 command is very simple and requires no extra parameters. In this example, we will set a tool offset using G43 and then immediately clear it using the G49 code.
G43 H5 G49