[supahonkey]

I have a 1972 Bridgeport Series I mill with a 2J head. I am reassembling the mill from a complete tear down and rebuild. The quill is very tight in the housing upon reassembly. At this point, I only have the quill housing installed; the variable speed housing isn't not installed.

I did some research prior to writing this thread. When people had this symptom they were told to loosen the variable speed housing, move it around, then tighten it back up. As I mentioned, I don't have this assembly installed.

The quill has very tight when I installed it into the housing. I could get it in about 3/4" into the housingg before I couldn't by hand anymore. I then had to use a dead blow. With each hit I would see about 1/2" of travel.

The quill and housing are very clean. I used Makino spindle oil to lubricate the quill and housing. The quill skirt is brand new, clean and oiled. Lastly, ,the shaft and gear that move the quill up and down is clean.

[machintek]

At this point pull the quill out and look for scoring. the clearance between the quill and housing is .0004 inches.
I see you have the spindle in and quill nose. If you tightened the set screw on the back of the quill too much the quill eggs out and will be difficult to move. Remove that set screw and see if that helps.

George

[mactec54]

supahonkey

Does your quill housing have the steel tube spacers, inplace on the mounting bolts, & are they not over torqued, over tightening the 4 mounting nuts can make the housing out of round,

You should not be using a hammer to put the quill in, You will only do more damage

[supahonkey]

I haven't overtorqued the four bolts. I doubt the "overtorqued bolts deform the cast housing" idea. A quick look at the casting and the amount of material surrounding the bore for the bolts makes the housing a lot stronger than the bolts. Overtorqued bolts would shear before any deformation occurs. I just don't see it happening.

[mactec54]

supahonkey

I guess you no best then,& don't need any help, I have rebuilt many of these heads, & it is quite easy to deform the quill housing, if you don't know what you are doing, the clearance is normal at around .0004, but I have had them with .0002 & it takes very little for them to get tight/stuck, if not assembled correctly

There are other things that can cause the quill to get stuck as well, that just one that is common

You could just beat on it some more?? (thats sure to fix it !!!)

You should not be using a hammer to assemble any of these parts

[Bpt Service]

These other guys are correct. The quill housing can get distorted. I have done many of these over the years. This is the best way to attack this problem. Remove the spindle assy. from the quill...remove the quill from the head....remove the quill down feed shaft from the head...Now you will just be working with the quill sliding into the housing...If quill is tight to go in then you will have to polish the housing...Start with something heavy, like 100 grit then work to 220 grit polishing the bore...you need to keep cleaning the bore out, then try it..eventually you will get to the point where you can put the quill into the bore, but it is still a little snug..take one more swipe with the 220 grit then finish with 400...Bottom line is quill should fall out of the bore on it's own by gravity when you let it go... After this point you can put all back together...as per George's comments the set screw for the spindle nut has to be hand tightened only and spotted.

[machintek]

As a side note I received a head from NASA to fix. The quill would not move. It seems they wanted to use it on a robotic arm and pressed in bushings in the two lower quill mounting holes. Sure, they would not come out but there is a reason Bridgeport put those loose spacers in there, so the mounting force was against the back of the quill housing. These rocket scientists by pressing the bushings in, egged the quill housing and grabbed the quill tight.

George

[supahonkey]

Gentlemen,

I made a little bit of progress last night. I appears as though a previous owner didn't fully seat the set screw for the spindle nose. The set screw created some nice gouges in the housing bore. They start at the bottom and go up about .750. I used sand paper and removed the high spots on the score marks. I was then able to get the quill about 3/4" into the quill before I ran into another issue. There were a few weird looking score marks (they were perpindicular to the bore, not inline with it) about .250 below where the bore for the quill lock intersects with the quill bore. I used sand paper to remove the high spots.

The quill is now easily inserted up to the intersection of the quill lock bore and the quill bore. Suspecting that a burr was at this intersection, I tried to lightly sand down any high spots. I reinserted the quill but it stopped at the same spot.

When we say distored/deforming, are we talking about tight bolts temporarily deforming the housing? As in, the tight bolts deform the quill bore, but once they are loosened the bore returns to it's normal shape? I can easily see this happening, but permanent deformation from those four bolts seems unlikely to me. I tried removing the quill housing from the mill so as to make it in a free state. The quill still would hang up at the same aforementioned intersection.

I will try Bpt Service's method this afternoon when I get a chance. I am dying to get this thing done. All of the other parts for the head are assembled and ready to be installed... they are just waiting on this quill situation to be resolved.

Would spraying the quill with Dykem, installing it in the quill until it hangs, pulling it out, and then seeing where the Dykem was scraped be a good idea? Would most of the Dykem wear off since the fit is so tight?

Thanks for your help, I truly appreciate it.

[Bpt Service]

The casting will actually get deformed and stay that way. Usually creatd by someone really tightening the bolts too tight. The Bridgeport Spec is max 50 foot pounds. But, How many people do you see with torque wrenches on hand. What generally happens is the end user takes too heavy of a cut for the machine, this causes his head to move and go out of tram, he then re-trams the head and really hawks on those bolts, thus causing the distortion. Sounds like you are almost there...keep polishing then clean then oil up and try.