Last updated: March, 2018.
Original posting: March, 2006.
As part my scraping of a worn Bridgeport milling machine back to original precision, I had to disassemble the machine components. I had to repeat this disassembly later when I upgraded the leadscrews to ballscrews as part of my CNC upgrade project. Disassembling a Bridgeport mill is also sometimes necessary to move it into a small shop space or through a low doorway, or when using small vehicles.
You must be careful to not mar or force the precision dovetail way surfaces against each other when separating, lifting, and manipulating the heavy components. If you do accidentally mar the ways in a small spot, you must reduce this damage by marking against a precision flat and scraping. If you don't have the scraping tools and skill, you can approximate this technique by lightly rubbing a flat honing stone or precision file against the ridge that typically raises up around the impact point.
Here are the disassembly steps I performed:
Start by cranking the table so it is approximately centered on the saddle. The disassembly order then is: nut on right handle, handle, knurled stop, scaled dial, cap screws on bearing plate, bearing plate. Repeat these steps on the left end. Leave the leadscrew in place. Remove table gib screw and tap out the table gib using a thin rod against the opposite end from the gib screw. After the gib is removed, observe that the table will be only loosely engaged and captured on the saddle dovetail.
The table itself weighs 215 lbs (42 inch long type, no screws, gibs, endplates, etc; more for the the 49 inch size). Attach a hoist (I used a shop engine hoist and lifting sling through two eye bolts on T-nuts on the table, placing the eye bolts about 1/3 and 2/3 along the length of the table for balance and hoisting stability). Pump the hoist to lift the table just enough to suspend the table, such that the table dangles freely in the un-gibbed dovetail space. Then work the table horizontally off the dovetails by wheeling the hoist gradually across the floor.
If you have another person to help, but no hoist, you could bolt long handles (SuperStrut would serve well, or perhaps 2x4 lumber) onto the tee-slots in the table and lift as a team by hand, in the manner of carrying a body gently on a medic stretcher (or a king in a sedan chair!).
You can also slide the table onto a sturdy workbench instead of hoisting; crank the knee up or down to match the bench height.
Don't mar any precision surfaces. On these components, almost all surfaces are precision!
The gibs and ways will be quite a mess with oil or grease. The knee will likely be filled with old chips. Standard cutting fluids in the past were animal fats, so the knee may be harboring a residue with the aroma of an ancient abbatoir. Kerosene, nitrile gloves, and a carton of paper towels are good for cleaning this situation. The big polyethylene mortar mixing tubs sold at the building supply store are a useful "wash basin" for containing the mess of solvent-cleaning big parts.
Be prepared for surprises and mysteries. I discovered the overworn saddle gib on the old machine I bought had been shimmed ... with a rough piece of metal pallet strapping.
The original Bridgeport design provided lubrication to the ways with grease forced in through zerk fittings. Having the components disassembled is the best opportunity to clean out the lubrication passages and upgrade them with central oiling tubes and a Bijur type lubrication pump system.
If you want to refinish or paint an old machine, it is best done while disassembled. With automotive bodywork materials and techniques (grinding, filling, masking, spray painting), a modest effort will yield a finer cosmetic restoration than the original. A simple scrubbing followed by a thorough shpritzing with canned industrial spray-paint is easy and worthwhile, if you're after a respectable look rather than museum quality.