Bridgeport mill alignment between turret,ram and the column.

[bustamallard]

I have run into this before. The way I square the ram to the table is as follows: get a large angle plate (the bigger the better), and dial it in using the y axis and a dial indicator in the spindle (then clamp the angle plate down).
Then lock the table axes and run the ram in and out using the same dial indicator until the ram is parallel to the y axis. Leave the locking screws snug but allowing movement. Then lock everything down; it should be all good. Don't trust the calibrations on the column (or anywhere else for that matter). A few machining operations require this alignment.

 

[Richard King]

We are discussing rebuilding the ways of a worn machine by scraping the ways and not aligning the spindle or sweeping the head in now.

The way we are explaining it is close to or exactly the way the factory does it when building the machine new. The machine has to be square from the column (Z) up or it will not machine correctly. The table (X) and saddle (Y) has to be square so when you are machining a plate it has to be square.
It is like building a house and you do not check level, parallel and squareness as you build up by the time you get to the roof the walls could be off a foot. You have to measure everything. If you did not check the parallelism of the column ways they would bind up when moving the knee, if you did not square the knee, when you bore up the hole would be oblong and cockeyed, if the table and saddle was not 4 corner square, when you machine flatness this would be off. The multiplication of errors will make it impossible to machine anything true if you do not check this while building it.

As I said before you have to align the spindle head last after you have scraped from column, knee, saddle and table. The ram swivel and ram are not even scraped where it rotates or slides out as accuracy is not required on the ram when rebuilding. This is set at the factory and never see's any wear. After you have the X, Y and Z scraped accurately then you sweep in the head-stock. When we rebuild the machine we also rebuild the head before we do the final alignment of the head.