That was tramming the node or the Y axis in the pic.If I understand your question correctly, I would only tram a vise in if I was sure I would not be moving the knee up and down. Tramming the head to a piece in the vice would in fact align the spindle with the piece, but if that piece were not perfectly in the same plane as the table top (perpendicular to the knee's vertical axis) then moving the knee up or down would throw things off since the spindle travel would not be perpendicular with the knee's vertical travel. The spindle would be at a slight angle to the knee's vertical travel.
In thinking about this more, if that alignment bar you are tramming isn't perfectly parallel with the table top (and therefore the Y and X axis travels) if you were to face a work piece with multiple passes, the facing tool would leave steps because the spindle is not trammed to the table's travel. The farther off the alignment bar is from being parallel to the table top, the worse the steps.That was tramming the node or the Y axis in the pic.
Indicate the work holding device, in this case a vice, do not assume that a $1200.00 Kurt vice will hold the .0001" parallelism that people are looking for, doing so on a hobby mill is a tall order.Hi Guys,
If you are going to tram the head, you really need to use the table surface, particularly if your mill is adjustable for nod as well as angle. Have you actually checked to see if the bed is truly flat and doesn't have any twist in it ? Once you have then you can tram the head in both planes and be reasonably sure it is square to the table.