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ljchipmaker
05-07-2008, 08:54 AM
I realize that I will not be able to provide enough information to make an exact estimate possible, but I need to know what price range a Bridgeport vari-speed mill would be. There is one going to be at an auction nearby and it looks like it is in pretty decent shape and I think also has a DRO. I have only seen a photo, so exact condition can only be guessed at, so any help here would be a great help.

Thanks,

lj

pcarpenter
05-07-2008, 11:00 AM
Age and condition are everything. Make sure the DRO works etc. Pull the one-shot oiler and come back 30 minutes later to see if oil is oozing out all of the way surfaces (table to saddle, saddle to knee, knee to column). If not, you can be sure its been worked a lot without lube. Most folks will tell you to check dial runout. Its somewhat meaningless without the ability to adjust and then check. The feed nuts are split and adjustable. This "test" may only tell you its out of adjustment. I would look carefully at the feed screws. If the "lands" on the acme thread are wider out near the ends of the table than the middle then the screw is worn in a fashion that will never let you adjust for a consistent fit from one end of travel to the other. They commonly wear in the middle where they are used most.

I got my BP on Ebay which is an even more risky proposition. Its a nearly blind auction--even if the photos are good. My late 1970's Series 1 2HP variable speed with a Newall DRO (that added a good bit to value in my book) cost me just over $3k. That's probably a stretch but it was listed as having been rescraped 7 years prior. I could not quantify what that would really mean or how well the job was done at purchase time. It looked filthy and was missing paint, but I fully intended to go through it from stem to stern. I found a bucket full of swarf inside the knee casting.

When I got it, I found that it had re-worn the saddle to knee ways enough that I wanted to scrape them back in. The other way surfaces were in good shape. I also found that it had new bearings just about entirely through the head. I found newer bronze feed nuts and new feed screws with "HQT" stamped on them (High Quality Tools...a supplier of parts and machine service), so in the end, I think it really had been rebuilt stem to stern. I tell all this to indicate that while I was a bit frustrated at having to do any scraping on a mill at 3k+, in the end, I think I got my money's worth.

On the other hand, I have seen them (usually sans the DRO go much cheaper).

Paul

lazlo
05-07-2008, 11:35 AM
I need to know what price range a Bridgeport vari-speed mill would be.

$500 - $5,000, depending on the condition of the ways, the leadscrews, and the spindle bearings.

Seriously, I've seen some Bridgeports that were completely clapped-out, that had been cleaned up and looked pretty nice from first glance (or an auction picture). Dishonest machine tool dealers will take a powered Scotch-Brite disc to the ways and shine them up...

But unless you can look at the ways and see how much of the flaking has been worn off, and how much slop there is in the middle of the leadscrew (which means you need to adjust the gibs to check), you're not going to know.

The Bridgeport Vari-Speed is also problematic -- if the black plastic bushing has worn out, you could have some major issues to rebuild it. You can tell that in 10 seconds by just turning the mill on.

You also need to power-on the machine to hear the spindle bearings. Bridgeports take a pair of precision matched 7207 angular contact bearings at the spindle nose, and a replacement set runs $300.

pcarpenter
05-07-2008, 12:12 PM
The replacement of the plastic VS sheave bushings itself is not a major problem. They are plastic making them much softer than the hard chromed shaft they slide on, but also making them (intentionally) the wear item and therefore are considered a maintenance item. I did mine (needed or not) during a full tear-down so perhaps I would find the replacement more annoying if I were not taking the whole thing apart anyway.

I suppose it could be true that if they were allowed to wear so very badly that they wore through you could have some major issues. On the other hand, the thing would sound like a truck dragging a chain by that time :D I'm not saying its not some work to take the belt housing apart, but I hate to see an intentional wear item being cited as a reason not to buy a mill. Its a bit like not buying an otherwise great car because it needs tires or a muffler.

Paul

Fasttrack
05-07-2008, 12:23 PM
I don't know too much about mills, but one of the older bridgeports here at school - it is not a j-head - has hard chromed ways. I think someone said it came to the school used in the early 90's or late 80's. It probably came out of a boeing factory, they donate alot of used machinery to us. Anyway, I was thoroughly impressed with the condition of the ways. The table is trashed, the t-slots are cracked/broken, but once I adjusted the nuts for backlash, the table moved end for end nice and smooth and the ways looked great.

Anyhow, seems like hard-chrome ways might be a nice feature that could drive up the value if it had them. Dunno which models would've had it or how valuable it actually is, but it sure seemed to make a difference. (Compared to another mill that does not have hard-chromed ways)

pcarpenter
05-07-2008, 12:32 PM
Hard chromed ways are a blessing and a curse. When they do eventually wear, it plays havoc with the rescraping process. While the knee way is hard chromed, the mating saddle way (by necessity) is not. The premise is that you have to have a soft surface bearing on a hard surface in order to prevent galling. What this means is that all wear is on the bottom of the saddle....a smaller total area, meaning it may wear more quickly. Even that has an upside however.

Since the saddle is smaller than the knee it travels on (its travel is fully inside the envelope of the knee ways), the knee normally wears low in the middle where its most commonly moved. This makes it swaybacked.

With all wear instead occuring on the bottom of the saddle (in the case of the hard chromed knee), the saddle theoretically will wear evenly over its life, meaning you don't have to normal problem of a loose knee to saddle fit in the middle when adjusted for travel out to the ends.

Paul

lazlo
05-07-2008, 12:48 PM
The replacement of the plastic VS sheave bushings itself is not a major problem. They are plastic making them much softer than the hard chromed shaft they slide on, but also making them (intentionally) the wear item and therefore are considered a maintenance item.

I suppose it could be true that if they were allowed to wear so very badly that they wore through you could have some major issues.

That's basically it: with any of the mechanical Vari-Speed drives, if you let the bushing wear down, the key or spline will tear into the female half of the pulley, causing major damage.

But because that happens inside the Vari-speed bore, you can't see the damage without taking apart the Vari-speed sheave, or just turning on the machine.

Fasttrack
05-07-2008, 01:57 PM
Ahh that makes sense. Like I said, I don't know too much about mills - i'm still working on getting a good handle on buying and fixing up used lathes. I guess hard-chrome ways are like induction hardened or tool steel ways on a lathe. Not a perfect solution to the wear issue but a pretty good one.

rmack898
05-07-2008, 02:18 PM
LJ doesn't say where he is from, but location is a big factor in what a machine is worth. The $1000 mill in the New England states will bring much more $$$$$ in a small town in the mid-west.

IOWOLF
05-07-2008, 02:37 PM
Yea, This is all to common here,No one wants to tell where they are , but want accurate info. Nuts just nuts.

ERBenoit
05-07-2008, 05:57 PM
That's basically it: with any of the mechanical Vari-Speed drives, if you let the bushing wear down, the key or spline will tear into the female half of the pulley, causing major damage.

You left the $$$ EXPENSIVE $$$$ part out of major damage. Shell out some bucks if these vari-speed discs get damaged.

I replace the bushings on the 2-J Vari-speed Bridgeport here at work every year. Needed or not. In the "home shop" the replacement thereof, of these bushings, may be far less frequent, and for significantly less than the cost of replacement parts.

Otherwise, as everyone else here stated, the age, condition, location, of the machine, as well as your desperation to have the machine, all factor into the "value" of any machine.

pcarpenter
05-07-2008, 06:01 PM
The key on mine (both the one I pulled out and the one I put back) was plastic. I wonder if that's a more recent change...perhaps something that's just included with these self-serve glue in bushing kits. Since my mill had been gone through before I ever had it, perhaps I never saw an original metal key?? Who knows, but what I saw allowed for no metal to metal contact unless you literally chewed through both sides of the plastic bushing and completely ate the key. I would think the whole works would become completely unusable before that point.

Paul

madman
05-07-2008, 08:51 PM
I have a 1961 step pulley B Port ./ I paid 1900 for it 15 years ago. I then spent another $1400 for a mitutoya dro and 600 for bearings and some other stuff it needed. NOW foraround $5000 you can buy a low hour First heidehain DRO 3 axis xyz and also Power Feed in X axis. These are nice but i still feel the b ports are better. Sometimes its worth xtra for something nice from the start. Also if you have a vfd and step pulley head i think this would be very nice also

ERBenoit
05-07-2008, 09:28 PM
The key on mine (both the one I pulled out and the one I put back) was plastic. I wonder if that's a more recent change...perhaps something that's just included with these self-serve glue in bushing kits. Since my mill had been gone through before I ever had it, perhaps I never saw an original metal key?? Who knows, but what I saw allowed for no metal to metal contact unless you literally chewed through both sides of the plastic bushing and completely ate the key. I would think the whole works would become completely unusable before that point.

Paul

The mill where I work saw no "real" care or maintenance other than oiling before I started there. The vari-disc drive on the motor had a steel key with a plastic "U" channel around it. The plastic "U" channel was completetely worn through, as was most of the key, rendering the vari-disc destroyed. That is how I learned these parts are not cheap. There is no bushing replacement kit for the motor mounted vari-disc. When the bushing in the motor mounted vari-disc is shot, so is the disc and $500.00. :( The motor drive key that comes in the bushing kit is still a steel key with the "U" channel to take the brunt of the force. The key on the spindle vari-disc was plastic, (as best I can recall) since I first started replacing the bushing kit yearly. As you mentioned, there is no metal to metal contact between the spindle and the vari-disc mounted thereto. If you do end up with metal to metal contact between the spindle and vari-disc, you should have been looking for the source of the noises that indicated something is wrong long ago.