View Full Version : Bridgeport question

01-17-2006, 12:27 PM
Hey all, havent posted much in a long time, I haven't been stateside.

Question though, I just "inherited" a J-head (i think) bridgeport mill. It had been left outside at the former owners house for a week so it had some slight surface rust on the bed. I tried my best to nix it with a brillo pad and some denatured alcohol but theres still an ugly stain (im vain, what can i say). Does anyone know a better way to clean this without damaging the bed?

Also, the head is currently swiveled upside down (quill facing straight up). For the life of me I can't figure out how to flip this thing over. The top of the head is currently resting on the bed with a sheet of plywood between them.

P.S. THose things are a *&$%#@! to move.

01-17-2006, 02:30 PM
The head should have a lock you loosen , then you can adjust the head to angles or straight. I do not know this mill , but mine does this too.
Having the head upside down is good to transport ...
Randy did a great rust removal tutorial on rust removal , using naval jelly and steel wool...Cant imagine that will hurt it ...
Hope this helps
The head might have bolts around it on a flange??

01-17-2006, 03:18 PM
On the ram behind the head there is a bolt head this is the drive for the gears that drive the head around loosen the bolts that hold the head to the ram and rotate the bolt with a socket wrench, the head is gear driven and will start to rotate in a direction (if this is a J head) now you get to figure out how to tram a head into alignment.
Oh yeah almost forgot don't losen the "Nodding" portion of the ram if you don't have to, it can be a real bugger to get them back in when both are out.

01-17-2006, 03:35 PM
You are getting good advice, but I would recommend lowering the bed first if you haven't already. You may want to "help" the head around as you turn the drive bolt...john

01-17-2006, 03:56 PM
JUst to add also , is every thing usually has a lock on it to kep the ways stable.
before you move anything unlock these locks . most are like a lever

01-17-2006, 04:30 PM
oil the ways before you try to move anything.

01-17-2006, 04:36 PM
There is a pin in the side of the ram near where you turn the elevating screw to rotate the head. It has a knurled end on it and it is in a little steel block. This pin is a safety to prevent the head from rotating past 25 degrees if the elevating screw breaks.(I've seen it happen, bad news) When you get back close to 25 degrees, you have to pull this pin out or the head won't go all the way up. Put it back in when you get past the 25.

01-17-2006, 05:27 PM
Some day I will figure out how to post a tutorial on tramming(indicating) the head on a turret type milling machine. It is a lot easier to explain in person and once you get the hang of it, it's pretty easy and only takes a minute.

01-18-2006, 12:24 PM
Thanks for all the advice. I used the rust removal tutorial witht he naval jelly and steel wool and aside from the pits already in the bed, it now gleams.

Finally got the head turned around, that was way more work than I thought it would be to find the right screws.

Now I just need to finish my 3-phase converter for the mill, surface grinder(chevalier) and lathe (chinese 6 foot bed). Then I can find new and interesting ways to endanger my fingers off the clock ; )

01-24-2006, 02:15 PM
I cut my eye teeth on a J series Bridgeport mill. Look at the serial number--it starts with a J...

Retired Tool and Diemaker with 30 years in the trade..

Mark aka Abonecoupe31

01-24-2006, 02:37 PM
I have a serial listing for Bports, if you give me the serial number I can tell you the year it was made


01-24-2006, 02:43 PM
Are the ways hard chromed and scrapped? The hard chrome protects the cast iron ways from wear and tear and its only a few thousands thick but very hard. The scrappings look like little "u" or "j" and they hold oil onto the way surface to lubricate the saddle, table, knee. Does your mill have a 1 shot lube system? if so most of the time their mounted on the left hand side of the mill with little tubes going to each way. Just depress the lever once or twice before using the mill and after each use i like to unlock my knee, and both tabe locks. If you have alot of play in your table, both "x" and "Y" or also the knee, their are gibbs that you can adjust. look for a slotted screw and very little tighten the screw to remove most of the play. If you can move the handles on the x and y and see alot of back lash, then the brass nuts are shot and they need replaced.

03-05-2006, 05:47 PM
I am also a Machinist, for 36 years. I work here: Erickson Aircrane ( Google it to see what we maintain)

In the simplest statement

tramming a head on a Bridgeport or any other knee mill for that matter, machine in neutral, quil out about half way and an indicator mounted that can sweep the table from front to back and side to side adjust concerned axis of pivot by observing the indicator.
This is one of the practical tests we give all new machinists.

Difficult without practice.

03-08-2006, 04:41 PM
Tramming is not too difficult. Develope a proceedure and stick to it. Use an indicator (preferably a test and not dial type, tho' it will work OK). Use a parallel of some sort(only need one, a gage block, 1-2-3, etc). Position table so center tee slot approx under spindle c/l, mount indicator and set indicator off to right and zero it upon your parallel. Now swing it to the left and slide the parallel under the indicator. This saves the indicator from pounding about on the tee slots. Adjust the head side to side first and get it with in say .005 and rezero indicator. This is quite easy as it is a 1to1 ratio(if 0 on the right and .022 low on left you crank head up on left .011 and you will be close on right). Now check the fore aft tram at the front and simply adjust the head til near zero. Too many times people get confused trying to get all 4 positions at once. If you have the head with in a degree on the nod axis(according to the engraved/placard degree tape) the error in the side to side reading will be minimal for now.If you are zero side to side you should be very close when you adjust to a zero at front. Once these 3 positions read within .001 now sweep all 4 quadrants. Don't make your adjustments using the back reading...this is closest to the pivot and quells the amplification of movement. if you adjust the "nod" at the front position you get an amplification effect as it is farther from the pivot. Now you can fine adjust to get 'er dead nuts....til you tork on those 4 nuts on the front :D . But once again, do not attempt to ste a zero off the nod axis....go back establish a zero off the side to side axis and adjust the nod at the frot based on this zero. Theoretically thes 3 positions are all that is needed, but when they do agree go ahead and sweep all four.
Another hint ...when you are with in .003 forget the side to side adjuster....there's so much slop in the worm it gets goofy. Simply place the worm slack and smack the top of head housing with the palm of your hand. As long as the bolts are somewhat less than tight you can get .0005 with a rap.
After doing this 4 times a day for 27 years in mold making it takes about 3-4 minutes to bring a Bridgie in after being off axis 5 degrees in both axis.
BTW.....please bring the ram in tram....many people overlook the effect on twisted turret has on off axis work.

03-08-2006, 04:48 PM
BTW.....please bring the ram in tram....many people overlook the effect on twisted turret has on off axis work.

To put that in laymans terms, do you mean the head inline with the top arm?


03-08-2006, 08:45 PM
To put that in laymans terms, do you mean the head inline with the top arm?

To accurately use the head off of vertical axis (IE: say a 20deg hole angled from top left of workpiece thru to lower right) the ram (the large casting to which the head is attached and in which the Bridgport name WAS :( cast) MUST be perpendicular with the X axis (the long side to side movement or table). The ram swivels on the main machine body thus is the turret axis. In the aforementioned example, the hole should have a common value in the Y axis ( say 2.5" from front face of our block) for the entrance AND exit at the bottom of workpiece. Lets say we tilt the top of the head over to the left at the aforementioned 20 degree angle. Imagine what the tilt would be if the ram were swiveled on the turret axis out of perpendicular with the X axis say 90 degrees over to the right(anti-clockwise when viewed from the heavens). Where would the cutter be pointed? Straight out the back right? We would be able to locate the top of hole but where is hole going to exit? Certainly not the same 2.5" from the front face of workpiece! It will be somewhere off toward the back since that's where the quill is pointing. We would have a 20 degree hole whose axis is no longer parallel to the front face of our workpiece. This is a rather exagerated example, but it does demonstrate what difficulties one can make for themselve.
If a fellow is always doing work with the quill/ spindle vertical this is no matter. But if you wish to do accurate off vertical axis work the ram must be aligned perp to the X (the table). I am sure this is cornfusing, but hope it helps.

03-09-2006, 01:44 PM
Thanks Joatmon. That was a good explaination. I was thinking of using with the spindle verticle. Tilting the head changes everything. Thanks again.