Y axis pre-alignment

[luizdiefenbach]

hello, I`m about to weld the last part of my gantry mill before I send to stress relief.

I have 3 set bolts on the Y axis so after welding I can fine pitch and roll the axis in reference to X axis, but I cannot Yaw. The fine tune of the Yaw will be on the X axis itself.

I would like to weld with minimum error possible, so with minor adjustment on the set bolts I can square the gantry.

How can I do this pre-alignment to tack weld the Y axis as near as possible square to X axis?

Sorry for my rusty English