RoyJ writes:

What were you picking up from the pix to indicate wear? I'm in the
market for a brigeport, always ready to get tips to spot the dogs.

Those knee ways are *the* major wear point for the Bridgeport machine.
The very ends do not experience wear since they're near to (or past) the
range of travel. Most of the wear is in a swayback pattern around 1/3
and 2/3 up the knee ways where the saddle rests on two bearing areas.
You can always see the crescent-moon scraping marks, testifying to the
original precision surface, at the ends, but depending on the degree of
wear, these marks are more or less worn off towards the middle. On this
particular machine, the photo shows they are completely obliterated
except at the very ends of the ways, indicating extreme wear, concave
where it should be flat. The mating surface on the saddle will have a
somewhat conjugate wear shape, convex where it should be flat.

If you remove the table and saddle, you can place a machinist's ruler
(the kind that has a precision straight edge good to a few tenths of
thousandths) on edge along the ways, and measure the deviation. On an
old machine like this, you will find concavity of several thousandths or
more.

With this degree of wear, if you adjust the gib with the table
positioned at the center of travel, the dovetail ways will bind up and
not move after a few inches. If you loosen the gib to allow more
travel, the table will be loose in the worn areas. Thus, the machine
has either lost its rigidity, or its table travel, take your pick, and
since you need both to do most machining tasks, the machine is broken.
It is not merely that you lose dimensional precision or squareness; you
either have motion but no rigidity and thus can't cut, or you have
rigidity but no motion and thus can't cut.

There's a similar process with the wearing of the table ways, but since
the table is much longer than the knee, and is protected from chips and
dirt, the wear tends to be slower and spread out more and thus is not
the limiting wear factor compared to the knee ways.

The usage pattern over the years can alter the process. If you run the
table left and right with a power feed all day, while the cross feed is
locked, then the proportions may be different. But typically the knee
ways are well worn before the table ways are.

The leadscrews likely have corresponding severe wear, and these are not
reconditionable.

The scoring shown in the photo is also extensive. A few dings, scores,
chips, and even oops-drill-holes do not ruin ways, but if they're
covered in scores, then the surface is way past being a bearing surface
any more, and can't maintain lubrication, so you have runaway wear.

I bought my Bridgeport machine cheap, realizing it was well worn and in
need of reconditioning by a laborious scraping process. On
disassembling the cross-travel gib, I discovered that the wear was worse
than appearances: The gib, long past its adjustment range for wear, had
a shim, consisting of some steel pallet strapping, shoved alongside it
by the previous owner. The mating dovetail was ruined.

With scraping, and epoxying on Teflon bearing surfaces, and $$$$ for
some new ballscrews, my machine now works better than when it was
factory new.

Note that the photo of the OP's machine was very clear and in high
resolution to show the state of wear. Most snapshots would not give you
enough to diagnose the degree of wear on the ways.