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MikesAuto
08-05-2006, 02:28 PM
Hello All-

This is my first post to this forum, I have been "lurking" for some time and I am impressed with the amount of activity, knowledge, and general friendliness here. I also frequent some shooting forums, and some of them have turned downright nasty, to the point I almost never post on them.

I have about 18 years experience as an engine machinist and builder, operating boring bars, Sunnen hones, crank grinders, valve and seat equipment, lathe, etc., but I have an opportunity to purchase a Bridgeport mill and need some guidance. I have almost no experience with vertical mills, I am looking at this one more as a machine for "one off" personal projects, with speed of production not being a factor.

The serial number of the mill is J-48986.

It also has a shaping attachment, serial number E-12369. The shaping attachment appears to have been added, as it is green and the mill is grey.

Do the serial numbers give an idea as to date of manufacture?

The mill has a power feed on the table.

My main concern: Before purchasing, are there any areas that I can check out without major disassembly that can provide some clues as to the condition of the machine? I realize that this is an old piece and may need some reconditioning and TLC, but I don't want to get into major headaches and expense.

The machine has sat unused for several years, and is located about two miles from my shop. I am in the position of being able to make an offer on it. I want to be fair to the present owner (and to myself as well). Any suggestions on a reasonable price?

Thank You in advance, Mike

John Stevenson
08-05-2006, 02:38 PM
J-48986 is the head number which can be any date as they never ran in line.
Some heads were sold on their own to other makers and some machines like the tracers had multiple heads..
The machine number is stamped on the front of the knee, slide the sheet metal guard back and it will start with a BR suffix.

Here's a list of the serial numbers.

http://www.metalwebnews.com/howto/bridgeport/bridgeport.html

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Leigh
08-05-2006, 03:39 PM
...slide the sheet metal guard back and it will start with a BR suffix.
Actually, I believe it will begin with a BR prefix.

Or are you on the other side of the Greenwich Meridian :D :eek:

Millman
08-05-2006, 03:42 PM
{{Actually, I believe it will begin with a BR prefix.}} Leigh, you're on the ball today; Can't believe I missed that one.

John Stevenson
08-05-2006, 04:48 PM
Prefix in the west Suffix in the east :D

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Boucher
08-05-2006, 05:23 PM
About seven years ago I gave $4000. for a 9 X 42 with X axis power feed and a 2 axis dro. It included an 8" yashika vise and Rotary table a good set of collets. The mill was pretty well worn. This was a step pulley machine.

About three years ago I purchased a 9 X 42 Variable speed with power feed and dro in mint condition for $2300. No tools. I in turn sold the old machine to a friend for the $2300. Keeping the tools.

This is a rural area so I don't have any how these prices relate to where you are. For what its worth I like the step pulley machine better than the variable speed. I think the VFD on the step pulley machine would be the best of both worlds. Keep your eyes open. Read the classifides and go look if something is intresting the good deals go fast. Jump in and get your feet wet you have to start some where.

MikesAuto
08-09-2006, 12:58 AM
Thank You for the info! I'll let you know how the deal plays out.

Mike

giddingm
08-10-2006, 07:27 AM
A few things to check.....Check the cross slides on the Y- axis....you want to see if the scrape marks are still there from the original fitting of the slides..Check the back lash on the dials....should only be 30 to 40 thou. This will indicate the amount it has been used( wear on the lead nuts.).Grab the table on the end with both hands and jerk the table back and forth....this will give you some idea of how loose the gib is.And of course if there is power to it,Run the head.....It will probably need a good lube job.Good luck Mark.

pcarpenter
08-10-2006, 11:31 AM
I see people mention slide dial runout a lot as an indicator of wear and suitability for use. Ignoring the fact that you can use a tool with lots of dial runout, there are two thoughts I would offer.

The cross feed acme nuts are held in their bores by a screw head. This can be adjusted in to compress the acme nut which is slotted. This is so you can adjust out runout. The nuts really need to be cut completely in half to have much adjustment at all as compressing this nut is pretty difficult. Soo......a machine that may be really just out of adjustment may feel "worn out" when it is not.

My BP had *huge* amounts of runout in the y axis when I picked it up. So much so, in fact, that I suspected a missing nut lock screw, and indeed that was the case. If someone walked up to this machine, they would have concluded it was worn beyond use. In point of fact, it had recently had new screws and new nuts. I made a new screw and it can be adjusted with very minimal runout. Now that I took it completely apart, I went ahead and split the nuts the rest of the way with a hack saw and cleaned up the faces on the lathe. This will allow for *lots* of adjustment over the life of the mill.
Paul

Leigh
08-10-2006, 11:39 PM
The cross feed acme nuts are held in their bores by a screw head. This can be adjusted in to compress the acme nut which is slotted. This is so you can adjust out runout. The nuts really need to be cut completely in half to have much adjustment at all as compressing this nut is pretty difficult.
This aspect of the Bp varied considerably over its lifetime. Originally both the X and Y axis nuts were split and adjustable.

Later the Y split nut was replaced with a solid part and the adjusting screws eliminated, although the holes were bored and tapped for them. If adjustment is required, you remove the nut, saw it in half, replace it, add two new screws, and adjust as needed.

I believe the latest version of the machine has no split nuts installed, so the above procedure must be followed for each axis.

IMHO it's much easier to install a DRO and ignore the dial calibrations.