Is your bridgeport making cuts that are not vertical? Different length drills hitting your workpiece at different center points?
Sounds like you need to indicate the head in, so it is perpendicular to the table.
You can use a square on the head or quill, or just use the 0 line on the scales to get close.
For quick indicating of the head, I like a back plunger indicator with a wide point(keeps the point from falling into the Tslots). A bent rod held in a collet works well to hold the indicator, -attach the indicator so it is ~4 1/4" from center of the spindle, or ~1/2 width of the table.
Do the Y direction first. Turn the spindle and zero the indicator at the back of the table. Rotate the spindle and move the head a little past zero(the head is also moving up/down and zero will change). Move to the back and repeat until you are zeroed front to back.
Now check the X direction. Pretty much the same here as for the Y direction, except that you only want to move 1/2 the difference in indicator readings.
Recheck the Y direction. Hope this is helpful. Pat
Don Speice of Sparro.com added the following:
I like to use a set of 1-2-3-blocks. Slide a block under the indicator, swing the indicator holder to the opposite side and slide the other block under. And just do 3 points. Left and right on the X, then either front or back on the Y. And don't kill yourself, .001 in 8 inches is plenty good enough! A good tramming and indicating tool is the 1st Word Indicator Holder, at www.sparro.com/1st_word.htm"
Thanks Don, I like the 1-2-3 blocks idea. Not to take anything away from Don's addition, personally I still gotta go with Y back and front first. The rear position, being closest to where the head pivots on the ram, will move the least. The front position will move the most. Therefore, zeroing the indicator at the back and taking care of the Y direction first should speed the process. Hope everyone finds a way that works for them. Sparro has some neat tools, checkem out. -Pat
PS: Have something to add? A helpful tip for others? E-mail me I just might add it.