Stiff Quill

[kmacht]

I need some advice. I bought a J-head bridgeport a few weeks ago. It had been used in a plastics company previously for a dedicated operation. They had a rotary table on it and just put the part on the table, cranked the knee up and took their cuts by rotating the rotary table. The X,Y, and Quill were all locked in place. I obviously want to use it as a normal mill. I was able to free up the X and Y axis by cleaning out all of the junk accumulated on the lead screws and ways but am having a problem with the quill. It is stiff to move up and down almost like the quill lock is engaged. It gets stiffer as the quill travels down. I loosened the quill lock and tapped on it with a drift but it didn't seem to make a difference. I'm not sure where to go from here as I have never disassembled a j-head before. Is there a way to pump oil through the quill to try and flush it out? What is involved with removing the quill?

Keith

 

[kpotter]

I am going to run through a list of things to check. Is the power down feed off. Is the Quill gaurd damaged and dragging, it is the thin steel plate that is behind the threaded rod with your depth stop. They get bent and they drag and cause all kinds of trouble. Is it binding when the quill is all the way up and then is loose once you get passed a certain point, if so they may have overtightend the spindle bearings and distorted the quill. Is the return spring working? Sometimes it gets bound up and can cause drag, there are bushings that can get worn out and then they get out of alignment and cause drag. These are all possibilities but the most common is the quill gaurd is stuck and making it stiff. You will need to pull the top of the head off and take a look. The guard has some little tabs that break when removing so be carefull.

 

[Avrgjoe]

I have several mechanical drawings of the J-Head if you think they will help. They have been very helpful to me. They consist of Original drawings from Bridgeport Mfg. and exploded views, both with parts list. I was going to just post them here but they were too big. PM me if you would like them and I will E-mail them to you.

Joe

 

[kmacht]

Is the Quill gaurd damaged and dragging, it is the thin steel plate that is behind the threaded rod with your depth stop.

I'm not sure. It doesn't appear to be damaged from looking at it from the outside but I can't be sure. Is it supposed to move up and down with the quill? I noticed when I get the quill all the way down there is a gap where that piece of metal is and I can see the top of the quill and down into the bore where the spindle is. Not sure if that is normal or not.

Is it binding when the quill is all the way up and then is loose once you get passed a certain point,

The quill is looser when it is all the way up and gets tighter as it goes down. It is still stiff all the way up but not as bad. It takes alot of force to get it to move all the way towards the bottom of its travel.

Is the return spring working?

As far as I know it is. It is hard to tell with the quill being stiff but it doesn't move up or down when I let go of the handle.

These are all possibilities but the most common is the quill gaurd is stuck and making it stiff. You will need to pull the top of the head off and take a look. The guard has some little tabs that break when removing so be carefull.

Any chance you have a picture of what I am looking for?

[/QUOTE]

 

[jhruska]

The shop had eight Bridgeports that ran 2 shifts. Lots of tapping so the quill had to be 'loose.'
Check the setscrew that holds the collet key. If it is in there and too tight the quill will bind in the bore.
Else:
Pull the quill, clean everything, reassemble. That's it.
Remove the two screws that act as stops for the quill skirt. Do that from the top. Note the location on each screw and put it back in the same location on reassembly.
Regards,
John

 

[kpotter]

It sounds like the gaurd has dropped down, when the quill is down there is usually no gap. The fit between the quill and housing is tight so any debris will cause trouble.

 

[jhruska]

When the tabs on the Quill Skirt are sheared off, the Skirt (guard) will drop and the top of the quill and the splined shaft will be visible. The Quill Skirt is confined to a
counterbore that is directly above the quill bore. The Skirt cannot fit between the quill and quill's bore. It will not be the reason the quill is tight or drags. If the Quill Skirt is mangled it may stop full retraction of the quill.
The bore depth (length) is only about five inches. This is a good reason to retract the quill and apply the clamp when milling.
John

Step pulley or Vari-speed?
http://www.practicalmachinist.com/v...lls-lathes/problems-rebuilding-j-head-204538/
http://www.practicalmachinist.com/v...es/bridgeport-quill-skirt-replacement-205222/

 

[rmsfla]

I had a issue when I replaced the spindle drive key ..
The lock ring on the end of the quill , the set screw on the back of quill was too tight ,causing a bind...

Rereading the post..
The issue is when it's all the way down...now that's the puzzle.

Robbie

 

[kmacht]

I got most of it disssembled yesterday and based on the ammount of chips and "gunk" I have found inside everything so far I am guess that is was is causing the stiff quill. Interestingly I haven't seen the quill skirt. I'm not sure if it dropped down and is somewhere inside the bore or is completely missing at this point. I almost have the quill out. I am struggling with getting the reverse trip ball lever out since it is broken off. I'm going to start another thread looking for suggestions on how to remove it.

Keith

 

[jhruska]

If the quill has been removed take your hand and reach into the bore until it reaches the counterbore. The quill skirt has a vertical slot that is aligned with the column. Sweep your hand inside the bore until this is located. Pull the edge up until the skirt rolls into a smaller shape and pull it out.
John

 

[kmacht]

After messing with the reverse ball lock thing for a few days I finally got the quill out. The quill skirt was all the way up the top with the tabs bent down. I'm probably going to have to make or buy one when I put it back together. The binding seems to be from gunk that has gotten in to the quill bore over time since the quill skirt left the bore open when the quill was more than 2" or so down. I cleaned it all out, oiled it up and it now slides nicely up and down the bore in the head. Thanks again for all the advice.

Keith

 

[ChevyCrawler]

Excellent advice. I can tell it's the quill guard without even looking. I see the bottom of it wedges up top. Thanks fellas.

 

[4GSR]

Woke up a sleeping thread..... Did you notice that was from 11 years ago?

 

[p-moon]

Yup old thread, but maybe I can share something that will help someone. When I had the shop, I liked all of the bridgeports to have nice, smooth unsticky quills. First thing that I would check for is an over tight quill nosepiece setscrew. If they are over tight, that will oval the quill enough to make it sticky when it is all the way up. That setscrew is a dog point and needs to be in a milled recess in the threads. If the quill was tight all the way, I would remove the nosepiece, and lightly scrape the bore of the quill to remove whatever was causing the drag. Usually happened after fine milling of hardened steel, and the very fine chips seemed to imbed themselves in the bore at the bottom.