As always reference the LinuxCNC manuals and the LinuxCNC Wiki for more information.
One of the most basic questions is how to I locate the material to get ready to cut? First you have to know how the G code program is referencing the material. Typically the left, rear, top corner is X0 Y0 Z0. This means that all the cuts in the X direction are positive, all the cuts in the Y direction are negative, and all the cuts in the Z are negative.
The next question is why set up the material like that? That is the fastest most accurate way to set up. The fixed jaw of the vise never moves once the vise is bolted down and indicated so it makes sense to use the front face as the Y0 reference in most cases. The X axis can go either way but for consistency sake we will use the left side of the material. The top of the material is the easiest to find so it is Z0. All of this can and will change to suit the machine, job etc.
To find the front face of the rear jaw of the vise mount an edge finder and turn the spindle on to about 500 to 1000 RPM. Slowly move the edge finder toward the rear jaw of the vise using incremental jogs no more than 0.010". When the edge finder is close to the jaw change to 0.001" incremental jogs. Exactly when the bottom part moves to the side stop the spindle and touch off.
Make sure that Machine/Touch Off to Workpiece is selected, the Y axis is selected and that the current coordinate system is G54. Now in the Manual Control Tab pick the Touch Off button and make sure P1 G54 is selected in the drop down box. Enter -0.100 in the text box and click OK. Notice the value is minus 0.1" as the edge finder is on the minus side of the jaw and it is 0.200" in diameter.
To find the X0 for the material place the material loosely in the center of the vise using parallels if needed to get the vertical height needed. Now load a dowel in the spindle and move the spindle so the dowel is to the left of the material and below the top and centered up in the Y axis. Now move the dowel to the right till it touches the material, push the material against the dowel and tighten the vise.
Now touch off as above but make sure the X axis is selected and you enter in a negative value equal to 1/2 the dowel diameter. You have just set the X0 location.
Load the cutting tool your going to use in the spindle and move it to the rough XY center of the material. Using a dowel as a guide lower the tool until it is below the top of the dowel. Push the dowel up against the tool and slowly raise the tool using incremental jog at a setting of 0.001". At the exact moment the dowel rolls under the tool stop and touch off the Z axis using the diameter of the dowel.
Now you have the material in the vise and have located the X Y and Z 0’s and it only took a short time.