hey gang, i have an opportunity to buy a 1977 bridgeport series 1 that
came from the factory as a CNC machine. this is an urgent request, as if
i don't drop the money by tomorrow morning, off it goes to a wholesaler.
needless to say, the price is phenomenal regardless. ($1500) here's
what it comes with:
the mill itself(9x42 table, varispeed)
sargon 2 axis DRO
rotary phase converter
whole buncha tooling
the original papertape contoller for the mill!
a mazak mazatrol cam m-2 controller seperate.
the machine has been sitting idle for 15 years, but doesn't have a spot
of rust on it. it is not under power, so i don't know what works or
doesn't. the hour meter only reads 140 hours, and from the condition of
this thing, i believe it really is that low.
so, since i'm not a CNC guy, and frankly an amateur hobby machinist,
what would it take/how easy would it be to convert it back to manual
control, OR to hook up the mazatrol and use the dials on it to manually
control the servos and make it work that way? effort and cost opinions
are welcome. if needed, i can send a zip file with pictures of the
TIA for quick responses!
Hmm ... at that period, it is probably a BOSS-3 (the first one
to escape the factory), and uses steppers, instead of servo motors.
Should be 12" Y-axis travel, if it is what I think.
A nice add -on.
Hmmm ... this I don't know -- but it well may be an improvement
over the original BOSS-3 controls.
It should also be chrome-plated ways on the machine, and you can
check for the flaking in the Y-axis ways.
Hmmm .... If it is what I think, it will be difficult to convert
to manaual controls for the following reasons:
1) he leadscrews are ball-screws, which don't co-exist with manual
operation very well.
2) The X-axis ballscrew does not rotate -- it is rigidly mounted
to the right-hand end of the table, and the ball nut is mounted
in bearings on the knee, and *it* rotates. (This minimizes
whipping when the machine is moving fast.
3) The Z-axis ballscrew is concentric with the quill, and the nut
spins around it. No provisions for hand feeding the quill.
Hmm ... I don't know the Maztrol package, so I don't know how
easy that would be, but I have used a Series-I BOSS-3 with just the jog
controls to move the table and quill. Awkward, but doable. Probably
the simplest thing, since these are probably steppers, is to make up
drivers which take step and direction information from encoders on
handwheels. The machine should have Veeder-root encoders on both axes
to tell the position in both X and Y -- but nothing in Z. Your DRO may
be a lifesaver in this.
Other than that -- one of the PC packages to drive the steppers
might be a good choice.
If it is a machine of the sort which I think the serial number
should be on the knee (perhaps hidden by the sliding chip guards), and
it should be a low number, starting with CNC, then several spaces, then
the number. Mine is "CNC 108", and I've been told that Bridgeport
started with "CNC 100". :-) If it is this low, it will probably be
controlled by an LSI-11, and a set of custom logic boards (which were
wire-wrapped, in mine. :-)
Why not put it in the dropbox (check out:
And then post here what the images are named. A bit of advice -- avoid
spaces in the filename and it will be more friendly to other systems
than Windows boxen. Also -- include a file with the same name as the
photo, but with a ".txt" extension, (with lines preferably not longer
than 72 characters each) which explains what the image is, and why it is
OK, it is a BOSS machine. It will be VERY expensive and difficult
to convert this to a manual machine. The X axis leadscrew doesn't
turn, the nut, buried deep inside the knee turns! The quill has
a ballscrew track ground into it, and the ballnut rotates around
the quill. It will be relatively easy to junk the control and
replace it with a PC and modern stepper drives, and have a very
nice CNC machine. But, I would forget any plans to convert back to
manual on this particular design of machine. It is NOT a manual
machine that was converted to CNC, as some other machines are.
The Mazak control doesn't really have anything to do with this machine.
it most likely is for servo motor control. If anything is missing
(motors, encoders, software) it will be thousands of $ to get it
thats exactly the type of analysis i wanted to hear. unfortunately, it's
not the answer i wanted to hear. oh well. i'll find one some day that i
can afford. just gotta keep using my little benchtop guy nutil i do.
thanks for the help!
Well, I guess it is too late for this one, but CNC is actually
quite neat. A PC and about $300 worth of stuff will make such a
machine run. You might even be able to sell off parts of the old
Bridgeport control. And, with CNC, you immediately have a
built-in DRO of sorts, if you choose to just move it around
manually with the jog keys. But, you can mill circular paths
and odd angles just as easily as cutting along the X axis on
a manual machine. All I can tell you is, I'll never go back
O.K. In numerical order:
1) It does not appear to have the pneumatic motor on the spindle
speed control which appeared in later machines, suggesting the
2) (Sideways image) It looks like it *is* the stepper motor on the
side of the spindle housing for Z-axis motion, which means that
it is BOSS-3 through BOSS-6 I think. (BOSS-8 went to servo
It does not have the Pneumatic actuator for the brake lever
(again neither does mine).
The motor direction switch, and the panic switch are mounted
differently than mine, FWIW.
3) O.K. The control pod says that it is BOSS-3 (or maybe BOSS-4?).
BOSS-5 and BOSS-6 have a different panel, with more displays.
4) I think BOSS-3 (though it might be BOSS-4). A bit later than
mine, because the serial ports have been relocated for easier
access. (You can see them under the telescoping protector for
the leadscrew under the table and to the right of the X-axis
stepper motor (big finned object)). The vertical orientation of
the belt guard for the Y-axis says that it certainly is not the
servo motors, but rather the stepper motors.
5-8) Images not present.
9) O.K. I don't know this one, so I suspect that is the alternate
set of control electronics, and it looks as though you could use
it with the cranks to emulate a manual machine -- once you know
how to set it up properly.
10) Another view of the alternate control electronics, with what
looks like the stepper driver electronics below the control pod.
11) A rather out-of-focus view of the whole machine.
So -- stepper motors not servos, LSI-11 CPU in the box on the
side (with punched tape reader in the top, usually).
The instruction set of the BOSS-3 is rather limited, and the jog
controls will move in steps of 0.001", 0.010", 0.100" or 1.000", and
nothing in between, so controlling it with the jog is a real pain --
though it can be done.
You'll be better off with the other set of electronics, if you
can find enough information to connect them to the steppers.
Note, also, that you can reduce the weight significantly by
removing the electronics box on the right and the transformers and
saturable reactors in the box of electrical stuff on the back of the
machine. You'll probably still want to keep the relay which handles
reversing the spindle motor. In mine, it is in a box bolted to the side
of the large box with the transformers and saturable reactors, but the
manual shows it inside the larger box.
There is one transformer in the CPU box which you will probably
want to keep -- to converts the 240V input to 120V for things like the
one-shot oiler lamps, and the punched tape reader. (Though I doubt that
you'll be using the punched tape reader for anything -- lacking an
8-level punch. :-)
I hope that this helps.