I've very carefully avoided learning too much about Bridgeports, because I
didn't expect to ever be able to get one - but my wife has just given me the
green light...so now I need to do a little learning!
Is there a Bridgeport FAQ? I'm looking used, in the $2k - $3k range, what
should I expect? Can you get a 220 volt single phase version? In a
non-production environment, is variable speed essential or will an 8 speed
belt change work as well, if harder to change speeds? What is essential to
use it to do valve seat work on automotive heads? What are good
alternatives to Bridgies, beyond the off-shore stuff?
Thanks, Guys, I want to get the right machine the first time!
I like the step pulley belt models with a VFD for speed control.
Its better than the mechanical vari-speeds since you get "instant" braking
I hardly ever change the belts on mine anymore, just sometimes put in the
If you're tight on $ you could start with a step pulley machine first and
add the VFD later.
Also if you only have single phase power available with a VFD you get 3
phases to the motor and full power without an additional phase converter.
A lot of the used machines you will come across will have 3 phase motors. If
you don't want to get a VFD but find a good machine that needs 3 phase
power, the "static" phase converters work ok for most peoples usage. You
only get 2/3's of the full motor power, but thats plenty for most machining
operations. Before I got my VFD I used a static converter for many years and
never had a lack of power, even taking pretty heavy cuts on steel. A static
converter (which is really just a capacitor and relay in a box) costs about
There are alternatives to a real Bridgeport that are pretty good- Lagun,
Sharpe, Gorton, and others.
Poke around on the web groups for some opinions on these.
In my opinion all the chinese machines are a big step down, although some of
the Taiwanese machines aren't too bad, especially the earlier ones.
One thing thats important is to be able to tell the difference between a
machine that's been used hard (ie production) versus one thats been in a
prototype or tooling shop and doesn't have a lot of miles on it.
Backlash, condition of the ways, spindle runout and general appearance of
the table and the spindle can usually tell you how the machine has been
Take your time and look at a bunch of machines before you buy and you'll get
a feel for a machine that's worn out versus one thats in good shape.
Probably the best deal today is to get the 8-speed (1J) model with the
motor, and use a VFD to get variable speed AND the single to 3-phase
conversion. The variable speed feature adds height to the machine, and
also some expensive and hard to fix parts that tend to go bad about the time
the machines are retired. This is what I have, and I have never really
the varispeed option (that is the 2J head). I can't, in fact, use a 2J,
top of the motor would be within 1" of the ceiling, and cause a lot of
For $3 K you should be able to get a very good machine. The klunkers
usually sell in the $1750 range, and can be anywhere from good but
rough looking, to very badly worn. Get the chromed ways if you can, they
are far more robust. Examine the ways for signs of wear. Also, at the
of travel on an axis, measure the backlash in the screws, by turning the
until the table moves, then turn the other way until the slack is taken up.
Then, repeat the measurement at the end of travel. If the amount of slack
differs, that is the differential wear in the screw from middle to end.
It also becomes a pitch error in the leadscrew, over roughly half the length
of travel, and therefore will limit the accuracy of any movement calculted
off the dials next to the handles. If it is much more than one dial
you will likely want a DRO, so you might as well find a machine with
a DRO already on it.
Changing speeds on the 8-speed 1J head is trivial, it only takes me 15
seconds or so.
Valve seat work? I think much of that can be done with a good drill press.
But, certainly a Bridgeport can do anything a drill press can do, only
(With the exception of drilling a hole in the end of a 5' bar or pipe.
are ways to do that, too, by swiveling the turret.)
The advantage of a REAL Bridgeport is parts are available anywhere in
for them, new or used. Some knockoffs have a number of interchangeable
some DON'T! And, you don't want one of those, in the event you have
major, like a casting, break on you. Also, the knockoffs may or may not
allow various accessories to bolt directly on without modification.
Specifically for valve seat work, I guess a fly cutter would be used to
the old seat and prepare the head for a new insert. Then it would be
cut the new seat to the proper angle. This could be done with carbide
in the flycutter. There are probably tools made specifically for this
if you'd be doing a lot of that sort of work.
Once you have the machine, you will find a huge number of other kinds of
work you can do on it. You might have a need for special fixtures, tools
and holders if you do a lot of engine work.
Thanks for the great info. I know that BP's get discussed a lot, but this
is such basic stuff that I was embarassed to ask, honestly. I have a
Harrison horizontal mill, but the BP is quite different. I have a friend
who uses them quite a bit, and he should be able to help me out here.
I'll look for an 8 speed as my preference, I don't like the idea of old worn
out vari-speed pulleys.