Rotating the g54 coordinate system.

Hi let's assume I have a work piece not perfectly square on my table. Could I touch of one side of the workpiece on two points with a probe. Then I would define this as one of the axis of g54 coordinate system. Let's say y axis. So that it would be rotated to g53?

yes, but I think rotation is applied to the current coordinates. qtdragon and QTplasmac already support part rotation the way you describe..
 

I've just implemented this for myself.

I already have autoprobe routines that set g54 parameters for X, Y, and Z. I augmented my autoprobe functions to log the x and y values of every completed probe, along with the g54 offsets in effect at the time.

When I have a rotated part, I touch it twice, along a surface that's parallel to its twisted X axis. That gives me two new log entries. I have a script that reads those entries, and calculates d = atan ( (y2 - y1) / (x2 - x1) ), after correcting the x and y values with the offset information.

The script prints the result in degrees. In fact, the script simply prints the necessary g-code: "G10 L2 P0 R $angle", which I then pasted into the MDI window.

pgf wrote:

I've just implemented this for myself.

I already have autoprobe routines that set g54 parameters for X, Y, and Z. I augmented my autoprobe functions to log the x and y values of every completed probe, along with the g54 offsets in effect at the time.

When I have a rotated part, I touch it twice, along a surface that's parallel to its twisted X axis. That gives me two new log entries. I have a script that level devil  reads those entries, and calculates d = atan ( (y2 - y1) / (x2 - x1) ), after correcting the x and y values with the offset information.

The script prints the result in degrees. In fact, the script simply prints the necessary g-code: "G10 L2 P0 R $angle", which I then pasted into the MDI window.
 
Once you generate the G-code command with the calculated angle, do you have any specific procedures for verifying the machine’s response after you paste it into the MDI window?

Once you generate the G-code command with the calculated angle, do you have any specific procedures for verifying the machine’s response after you paste it into the MDI window?