Bridgeport J1

[andrewbooker]

Hi, I'm new to the group and I have a question. I recently bought a Bridgeport J1 that has a crossfeed screw that was bent during shipping because they removed the handles. The company that sold it to me is sending a used screw to replace the bent one. The question is can I just back the screw out or do I have to remove the table to replace the screw? Later this year I plan on installing ground ball screws to convert the machine to CNC.

[79TigerPilot]

Just remove the nut from the crank handle, slip off the dial wheel and dial hub and remove the half round key. Loosen the 3 cap screws in the bearing compression ring to take the load off the bearing. Then take out the 4 cap screws that hold the bearing plate to the knee. Pull off the bearing plate. You will most likely need to tap the base of the little stop pin on the top of the plate from behind to get enough room to put a couple of screw drivers between the plate and the knee to pry off the bearing plate. You could also try putting a block of wood between the table and the column and running the table back against the wood to force the bearing forward. Its the two roll pins that are causing the grief.

Once you get the bearing plate off, you can look back in and see the yoke that holds the brass acme nut. (could be a 2 piece or single piece nut) The nut is held in and compressed to control backlash by a large headed slotted screw. Also there is a smaller locking screw to keep larger one from turning. Loosen both the locking screw and the larger retention screw, then screw out the lead screw. Screw in the new lead screw and reassemble.

You may want to pull the brass acme nut to clean it up. This may be a little difficult but it will come out, depends on how hard the crud is. There is an 1/8" key in the yoke to keep the nut from rotating. Note: the key is also pinned to the yoke midway down its length.

I just completed a total rebuild of my 66 Jhead, did a 100% disassembly cleaning, table regrind, ways scraping and repainting. I have posted some photos at: http://picasaweb.google.com/cschaffter/CNCMillProject#
There are a few pictures of the yoke and acme nuts.

Currently adding two 200 lb gas springs to the knee to take off some of the 617# of knee, saddle and table weight. Next the CNC stepper motors get installed.


Have fun.
Craig

[andrewbooker]

Thanks for the info. The machine has seen little use so everything is fairly clean. From what I gather it's possible the machine was made in England because the coolant tank is in the column. Looking forward to playing with it this Spring.

[79TigerPilot]

Just remove the nut from the crank handle, slip off the dial wheel and dial hub and remove the half round key. Loosen the 3 cap screws in the bearing compression ring to take the load off the bearing. Then take out the 4 cap screws that hold the bearing plate to the knee. Pull off the bearing plate. You will most likely need to tap the base of the little stop pin on the top of the plate from behind to get enough room to put a couple of screw drivers between the plate and the knee to pry off the bearing plate. You could also try putting a block of wood between the table and the column and running the table back against the wood to force the bearing forward. Its the two roll pins that are causing the grief.

Once you get the bearing plate off, you can look back in and see the yoke that holds the brass acme nut. (could be a 2 piece or single piece nut) The nut is held in and compressed to control backlash by a large headed slotted screw. Also there is a smaller locking screw to keep larger one from turning. Loosen both the locking screw and the larger retention screw, then screw out the lead screw. Screw in the new lead screw and reassemble.

You may want to pull the brass acme nut to clean it up. This may be a little difficult but it will come out, depends on how hard the crud is. There is an 1/8" key in the yoke to keep the nut from rotating. Note: the key is also pinned to the yoke midway down its length.

I just completed a total rebuild of my 66 Jhead, did a 100% disassembly cleaning, table regrind, ways scraping and repainting. I have posted some photos at: http://picasaweb.google.com/cschaffter/CNCMillProject#
There are a few pictures of the yoke and acme nuts.

Currently adding two 200 lb gas springs to the knee to take off some of the 617# of knee, saddle and table weight. Next the CNC stepper motors get installed.


Have fun.
Craig