Any tips on Bridgeports to get/avoid for a hobbyist?

[MychesterCNC]

I've looked all over Google and a few other forums, since Bridgeport seems to be the Volkswagen of Mills (as far as long-lasting, popularity, finding parts, etc...) does anyone know of a site or chart that lists the models and what's different between them?

I (like many people, I'm sure) have been watching for different Bridgeports for sale in my area, as I want to use one for a particular purpose, as well as to learn more about milling. I can live with manual chuck holders and manual tables, and i know the difference between 3 phase and single phase, but other things like "J Head" and so on... are there any huge purpose-type differences between them that might end up being a plus or minus for a hobbyist?

I just want to take slow minor passes, (But LONG and accurate, which is why I want to go with a bigger machine) and so any tips would really be appreciated, both about the features and the common wear points and what can be done about them, as I see that usually plays a big part in the going price.


ALSO: I'd really like to take LONG (42" or longer) passes- anyone know of a way to do that or extend/upgrade a table? Or where I might look for a new import table of extra long length?

[rockcliff]

The standard type bridgeport knee style mill, has been around for a long time, and it's hard to tell from a distance from one thats new or old, as the overall shapes of the castings are very close, if not identical

The J head is an older model of head that has step pulleys, to adjust the spindle speed, manually by moving the belt, it was a fairly reliable head, but with step pulleys you do not have infinate speed adjustment, as with a variable speed head.

Almost any head can be fixed, there are plenty of parts available for bridgeports, so you really need to check the stuff that's hard and more expensive to fix which are
1-wear on the quill,
2-wear of table ways,

Normally table slides will wear in the center, as most work is done in the center, so the table will become loose in the center and stiffer as the table is moved to the ends.


Not as comman but another good make of knee mills to look at is excello

hope that helps a bit, and hope someone else can put in their 2 cents too

[79TigerPilot]

I have to second what Rockcliff indicated.

Some things depend on what you intend to do with the mill and if you are going to convert it to CNC.

I wen't through the same thing about 5 years back. I have a 1966" step pulley J-head I got back in the 80's. Never really used it for more than a couple of odd jobs. Always had plans to convert it to CNC but didn't have the time until I retired. My CNC conversion is a works in progress but I am cutting parts with and couldn't be more pleased with the results.

If you will convert it to CNC you will want to get one with good ways or have them ground and scraped like I did (think $) also to really make it work you will want to replace the old acme lead screws with ball screws (think $).

I believe the better solution is to find an older CNC machine with a bad controller and convert it to Mach3 or EMC. The machine will already have ball screws and I am told will be easier to convert.

I would have gone that way if I didn't already have the 66 J-head in the garage.

Craig

[ad_bfl]

Look for a CNC machine with dead electronics, you will have a straight forward conversion.

[lancut]

"The J head is an older model of head that has step pulleys, to adjust the spindle speed, manually by moving the belt, it was a fairly reliable head, but with step pulleys you do not have infinate speed adjustment, as with a variable speed head."

Do like many did with the J head B-port. Not sure do you have a 3 phase power in your shop. If not, the get a VFD not only converts single phase to 3 phase but also give you infinite rpm control. As others said, converting older manual B-port to cnc cost more in the long run comparing to electronics repair/conversion of already cnc machine...

[Andre' B]

Here is a good bunch of info on Bridgeports.
http://www.lathes.co.uk/bridgeport/index.html
Page Title


"ALSO: I'd really like to take LONG (42" or longer) passes- anyone know of a way to do that or extend/upgrade a table?"

In my opinion if you need travels like that you really want a bed type mill.

[MychesterCNC]

Thanks everybody! I know that 99% of the "work" of getting a Bridgeport is to find one reasonably locally that I can get moved here.

Once here, I realize anything in my price range will need at least some fixing, and since I only need it for a few specialty cuts here and there, pulleys and manual machines are just fine for me.

I did see that "scraping" was mentioned in this post and a few others, so I guess there is a fix for a worn bed. And if I can find a machine that's beat, but cheap enough for me to fix and upgrade (and thereby enjoying the benefits of a newly "renewed" machine myself) then that would be ideal.

I wont be needing anything CNC or variable speed, just something that will be accurate for a few cuts here and there. But if I'm going to look for a worn machine and upgrade, not nessisarily for electronics or CNC, what kind of upgrades would you suggest? Are ballscrews only recommended if I will want to use CNC controlers?