# Bridgeport mill alignment between turret,ram and the column.



## LEEQ (May 3, 2013)

I'm studying up on restoration. Dry reading. On the vertical mills in the book, there is no turret and ram. When the machine is taken apart and laid on it's back the original bearing surface of the column ways are leveled and used as the datum point for beginning restoring the surfaces. Pretty important as the rest of the process keys off of this surface. With a Bridgeport style machine there are more moving parts in this equation. The turret and ram in specific. Are these supposed to be square to the column ways? When new, can you turn the turret and extend the ram without realigning the quill to the table? If so I would assume that this needs to be accounted for when scraping the column. If not I would think that with the nod and swivel of the quill housing being used to align it to the table, the column being perfectly perpendicular to this surface isn't necessary.  So my?'s basically are; Do the ram and turret move precisely in relation to the column ways? If so, what are common methods for checking this alignment?


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## sidecar580 (May 3, 2013)

In my experience... the ram and turret would not be used in a machining operation. The head would be squared to the table top after either of these two parts were moved. When rescraping a Bridgeport machine I would scrape the saddle flat and parallel first. then use the saddle and a straight edge to scrape the top of the knee. The back of the knee is then scraped and checked for square. I would then use the knee and a straightedge to scrape the column ways.

John Fahnestock


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## LEEQ (May 3, 2013)

I see. As laid out in Machine Tool Reconditioning Mr. Connely suggests going in order opposite to how you going about it.He cites that the column ,as the longest  bearing surface, is the place to start. I had no opinion about it but that made sense to me. Any small change of plane would need to be multiplied out over the longer surface of the column to make it square. I am curious as to why you go about it differently, not to say you are wrong, but because I will look at it from all angles. I have no experience only questions. Thanks for the info about the turret and ram. That would explain why they aren't scraped.


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## sidecar580 (May 3, 2013)

The column is  square with the top of the knee, and the knee is checked on a surface plate against a known square. The ram is only for positioning, and the head is adjusted to be square with the table top.
John Fahnestock


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## LEEQ (May 3, 2013)

Do you scrape the column last? Making it square to the knee. Or do you scrape the knee square to the column?  Basically, I thought you were saying you would scrape in the order you wrote it out. Saddle 1st then knee, then column. Is that right? Then would the table come first? Sorry, I want to make sure I understand.


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## sidecar580 (May 3, 2013)

I would scrape the table @ anytime...that has to be straight and parallel to itself. The knee has to be scraped square to itself...... and the column has to be straight.The saddle has to be straight and parallel to itself.

John Fahnestock


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## LEEQ (May 3, 2013)

I see where you are coming from now. Thanks for weighing in, I appreciate all the advice from people that do this sort of thing for a living.


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## Richard King (May 4, 2013)

I teach if the Mill spindle is stationary and can not be adjusted like a Horizontal mill you have to lay the column on its back and start there.  Connelly shows putting a straight-edge on the spindle and measuring from it.  I do something similar but I use a threaded rod thru the spindle holding a ground parallel to the spindle face and I indicate the test bar into the spindle rotation and shim under it so it follows the spindle bearings.  Then scrape the column and test to the spindle.  On a removable Head like a Bridgeport you scrape the column flat to itself following the original ways to guide you.  The tops dovetails  ways on the column are about an 1" wide and were machined at the same time the flat ways were machined, so I tell my students to use them as a guide to measure to keep the ways in the same geometry as the were when new.  

I also will first set the back of the knee on a granite table and scrape it flat and use it and a 36" camel back to alternatively scrape the column ways.  Sidecar and I do it in the same manner there.  I fit the dovetail and gib to the column before standing up the machine.  I do it a little differently to get the squareness of the top of the knee. I first grind or scrape the saddle as SideCar does and use a 24" dovetail Straight-Edge  and the saddle to scrape the knee flats on the machine and measure using a blade square or granite 3 sided square setting on the flats and crank the knee up and down and scrape the front of the knee .0003"/12" plus.  I do that to compensate for the sag when you put the saddle and table back on.  After that I pull the knee and scrape the dovetails flat and parallel to each other.  Then fit the saddle gib.  If it was a Horizonal machine I would scrape the doves parallel to the spindle.  

But on a Bridgeport remember the head removes so you need not worry about that.  Then match fit the pre-ground or scraped table to the saddle now you have to square the table travel to the saddle. I know this is getting a bit long, but there are a couple of ways I square it up, either on the rear top saddle dovetail if it isn't off to bad or I will do it on the saddle if it's off a lot because that way is shorter.  Then have to refit the gib.  finish the table and do that gib.  As Sidecar says the 4 corners of the table and saddle have to be all the same thickness.  When I am done, I lower the center 40% of the top and bottom of the saddle by .0005" to .001" so as the saddle wears it gets better.  Many of the of greased Bridgeport's had those areas relieved .020".  I'm getting writers cramp.  The bottom line here is there is always 2 + ways to skin a cat.   I told the wife next time I go to the lake I am going alone and will stop and help you.   Rich


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## LEEQ (May 4, 2013)

That would be great. I'm trying to find time to get down to springfield and pick up a surface plate and some other stuff before you get here. I think I'll order those gibs also. I'll be trying to figure out what thickness is necessary to build back up for leadscrew/ect. alignment so I can have that done beforehand also. I'm going to see if the machine will work as is for a while tomorrow. I shimmed the knee and saddle gibs. The stretched table gib seems to be just long enough before scrap[ing anything with the new table. It would be nice to be able to do a few projects with it.


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## Richard King (May 4, 2013)

Like I said before....what you are asking is a fix to make it better....a rebuild will take time and money.  I wonder what Sidecar charges for a rebuild?  Some call a fix up reconditioning.  I call a rebuild, replacing everything worn; bearings, belts, all scraping, new gibs or Rulon them, grinding table, repaint, new feed screws and nuts, updated lube system, updated electrics....With today's prices I would charge $7500.00 to $10,000.00 plus parts.  But still cheaper then a new Bridgeport.  You need to remember if we scrape off the flats and dovetails this will change the thickness of the gibs too.  Dropping the flats will make the dovetail open up.  If they are worn and flats are worn, we could possibly Rulon the flats and use your original gibs.   More to think about.


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## bustamallard (May 5, 2013)

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.


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## Richard King (May 5, 2013)

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.


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