How to decide if an old milling machine is good?

[crazyman]

I'm new to machining.
I want to buy a used Bridgeport series I or similar mill for a low price to get started. Then I want do a DIY CNC on the same mill.

Any suggestions on where to find this rare milling machine beast?

And once found, what should I be looking at to dertimine if the mill needs a total rebuild or not? (Prefer not to rebuild)
Is there an easy test that can be done to detemine accuracy? needs a rebuild?

[NEATman]

Crazyman-
If you are going to be converting a bridgeport to CNC, why not just purchase one that already is a CNC? It would save considerable time and money to go this route. These are available relatively cheap, at least here in new england. They can be purchased for $2-4000 US, or less if you are lucky. Plus, HSM (Home Shop Machinist Magazine) recently did an article about stripping down and simplyfing a used CNC bridgeport. I am currently doing this to a 1993 model V2XT which is servo driven. The great part about my machine is that the computers were unreliable, so this machine spent most of it's time sitting idle, so the machine is in great mechanical contition. I plan on upgrading the computer control, and I am researching servo drives and controls.

One way to tell the condition of the machine is to carefully look at the ways and the adjustable gibs that tighten the ways. On most of the CNC machines, the ways are hard chromed and all of the hand scraping on the ways is still clearly visible. Plus, CNC machines usually had the automatic oiling system, ensuring that the machinist didn't forget to oil the machine every few hours. Regardless if the machine is manual or CNC, if it has ballscrews or leadscrews, check the backlash of the screws. You can do this by hand, but a magnetic base dial indicator would give you an exact reading. Also, one other thing is to check and see if you can feel rotation of the table. To do this, crank the table to an extreme, unlock all of the locks, and push forward and back on the end of the table. If you notice movement, you can figure which set of ways is loose by the process of elimination using the lock screws.

If you do get a machine, manual or CNC, get as much tooling with it as you possibly can. Tooling adds up quickly! Plus, if it is a resedential location, with single phase power, you'll need a phase converter to generate 3 phases. Or, you could install a Variable Frequency Drive, and have variable speed without adjusting belts.

One thing that I am trying to do with my machine is to have it manual and CNC. 80% of the work I do is simple, and I want to be able to manually machine a part If I choose, and use the encoder output as a DRO. This is easier said than done, unless you have a Prototrack, or a Newall, which have this feature.

Here is a dealer near to me:
http://www.brothersmachinery.com/
They currently do not have CNC's, but do have several Bridgeports.

Hope that this helps!

[crazyman]

Thx for the quick feedback!
There is an old (1975 or so ) bridgeport cnc machine in my area for 2500Can.
Bit too much for me tho.
Also an english mill that has both horizontal and vetical mills on it for $1000.
Anyone have ideas on where I can get a <$1000 series I bridgeport? Do the Series!s come with servos?
How far back in time(Ie machine age) should I limit my self?

[HuFlungDung]

Crazyman,

Are you crazy?

$2500 is nothing, if the machine has ballscrews, servo motors and encoders on it. In fact it could be a steal, depending on the condition of course. If you buy manual and start converting to cnc, you'll be spending more than that in no time.

[BIG AL]

Crazyman, How about posting the guy's phone number that only wants 2500.00 can for the Bridgeport? (2500.00 whats that like 10.00 U.S.?)

[crazyman]

hehe...well see if it has servos... It may need some work but it also weight 5000lbs. I bit heavy to drah down the stairs to my basement.

Can- US exchange is $1Can = $.75US.

[NEATman]

Crazyman-
Trust me, if you really want to go CNC, you should get an old CNC and update it. The one that I purchased was an absoloute STEAL!! The machine is a 1993 3 axis Series 1 bridgeport, complete with flood coolant, automatic oiler, powerdrawbar tool changer, and imitation kurt vise. I am looking for NMTB-30 tooling for the machine, as it did not come with any. I bought it off a friend who had gotten the machine for FREE. He was scouting machine shops in our area to qualify them to make parts for our company, and commented on this machine in the corner of the shop, that was obviously not in use. The shop owner made an off hand comment that "it's yours if you get it out of here", and my friend had the riggers there two days later. All I paid for it was $600, to cover my friend's rigging charge. Plus, I helped him move his other two bridgeports and a large lathe to his new shop.

At this point, all I need to do is buy tooling, get software, and drives. Infact, all of the drives in the machine are fully functional, but do not accept step and direction control. They are the industry standard ±10VDC. If anyone has a lead on machine control software that is compatible with the ±10VDC input on my drives, please let me know. So far the only way for me to use the original drives with a low cost step-and-direction software is buying 3 R991H boards from Rutex. I may just replace the drives outright with new ones from rutex.

To get to this point starting with a manual would be several thousand dollars. There are many of these machines out there, and most people buying used machinery will want a manual machine. The CNC portion usually scares people away, especially if there are electrical problems. If you do get a CNC machine, check if it is stepper or servo. The 70's vintage bridgeport that you speak of was probbably a boss 1 with steper drives. There are retrofits available for either version of this machine, and I highly reccomend doing lots of reading on the subject. There are also several groups at Yahoo.com that deal with CNC and bridgeports. None of those groups could ever hope to compete with this site though!

[vacpress]

if i remember, there is some hardware the does a conversion of step\dir to control voltage. if not, 3 geckos would be worth it if the thing is DC...

[crazyman]

I looked at this CNC bridgeport last night I must say it made me drool to have it but the shear size does not allow me to put it anywhere in (or around..heeh) my house.
It has DC drives and all the self oiling pumps on board ands also needs 600V 3 phase power.
Sad it will not workout.

NEATman, you found an excellent deal. That is the size of setup that I would ideally like to have. An able to do both manual and cnc. What is the overall dimensions of the series I bridgeport? H?L?W?

[bob1371]

I went to an industrial auction and got a "91 Fanuc Drillmate with OMC controller for $1000.00. Got it home and everything worked great. Do some smart shopping and realize that sometimes adding things later really become a pain in the *ss
Bob

[NEATman]

Crazyman,
Here is a link to the www.mscdirect.com website that shows a simmilar style machine, along with the size and weight.

http://www.mscdirect.com/PDF.process?pdf=1419&Keyword=Y

As far as the manual/CNC the only machines I have seen with this capability are Newall, and Prototrak. The Newall machine was excellent because you can create a toolpath with a dxf file. At my previous employer, I even had them cut a spiral in aluminum for a specialized heatsink. It made using the machine extremely simple. I hope to have this type of functionality when I'm done.

Good Luck in your search. If you are looking for a vertical mill that can be dis-assembled and carried down stairs, and is still a versatile machine, try a small knee mill. They can be bought new for about $1500 US, and you could convert it to CNC at some point. I have a small mill like this also,and it's suprizing how much I can fit on it. To move it, it can be broken down into several pieces that are about 200# at the most. I easily moved it myself with nothing more than a 2 wheeled dolly. Grizzly sells several machines like this, and they are also available used on ebay. Here is a link that shows the history of this type of mill, and also here is the link to the Grizzly website, and the mill that I mentioned.

http://www.grizzly.com/products/item...A&site=grizzly

http://www.lathes.co.uk/clausing%20vertical/index.html

[crazyman]

There are few mill/drill machines that I can get new locally. They look similar to some of the grizzly mills in the website listed for about $1200-1600Can The brand is craftex. They also have small knee mills for 3500$Can
There are Vietnemese made tho. Are Vietnemese mills of high quality? Should I ignore these types and go with a second bridgeport?

Also. I will be looking at a vertical/horizontal mill on the weekend. I can get this one cheap. It is from the UK and is about 15-20years old. Any comments on the usefulness of this type of mill?

And...One more question.
The Vetical/horizontal mill takes #30 size rather than R8. #30 seems to be a better solution but for my hobby type needs, would it be cheaper/better to stay with an r8?