Checking Out A Bridgeport: What To Watch Out For.

[Metal]

Hey folks
I have a benchmaster, which I picked up for a few hundred, and completely refurbed (derusted, new spindle bearings, paint, ect. ect. ect. So this is not anything new to me.

I found a bridgeport (unknown table size so far) J head on craigslist for ~900 that I'll be checking out, apparently it is in "not good" condition, but the person wasn't very specific.

The plan would be to get this into my garage, grease it up and slowly disassemble/refurb the parts until probably late spring/early fall. From what I can tell I could be walking into a total frankenstein monster as bridgeports are mostly cross compatible between types(?)

Now is there anything I should be looking out for specifically for in bridgeports? I'll check the ways and backlash, but I'm not sure how to identify a worn out way if it is overall in good condition and not scratched to hell.

 

[Bob Korves]

Disclaimer: I have never owned, used, or put my hand on a M head Bridgeport... That is a very old machine, and much different than the newer and more common BP models. Various collet types were used in them, none of which were R8, which the later machines used and are the most common ones around today. The M head also has a lesser quill stroke, 3.5" vs. 5" on the later ones. The ram on a M head is round, a less rigid system. The table will be smaller than later models and has less range of motion. Parts will likely be relatively difficult to find. Upside, it is smaller and will fit in tighter spaces.

If you love vintage equipment and the smell of musty iron, and want a restoration project to mess with, go for it. If you just want to get a mill to use in your shop, get something else.

If the machine was in very nice running condition, and the price was lower, and you wanted a project to tinker with, then things might be different.

Do a lot of research before you buy that mill...

Edit: Not trying to diss the nice old machines that some of the members here might have, nicely taken care of, adequate tooling to fit them, and well understood by their owners. I love old iron, too!

 

[Metal]

Thanks Bob, good to know!

 

[chips&more]

Not trying to discourage you or owners of a M head…but. It’s a milling machine, yes. And it says Bridgeport on it! And made with good old USA cast iron too. But, that head has MANY differences as compared to a standard series I or II. Especially if the rest of the Bridgeport is an older style with the round ram. Sorry, I would walk away. Your day will come...Dave

 

[brino]

I found a bridgeport (unknown table size so far) M head on craigslist for ~900 that I'll be checking out

I believe I have seen the Bridgeport M-head mounted to "other" milling machine bases, so it could be a frankenmill.
That price seems steep for a machine described as

"not good" condition

Logic says that condition and price should be "proportional".

I'll check the ways and backlash, but I'm not sure how to identify a worn out way if it is overall in good condition and not scratched to hell.

My favourite "no tools" test for the ways is to move the table to middle position (or to the vise if one is installed) and tighten down the gib locks so the feed handle just cranks freely. Then try to crank the feed from end-to-end. Most wear happens in the middle (or near the vise), so this test helps to show how much wear there is in the ways. This works for lathes as well where the wear is mostly near the headstock.

-brino

 

[Ed ke6bnl]

I think I got the best of both worlds, price, and J head on a $500 Mill with a round ram frame. Yes the table is a bit smaller then some 9x36. But was able to sell my smaller Burke Mill for $1400, smaller ( great for some) and 110 volts. and DRO I added. I have since added xyz for the new to me bridgeport.

 

[Metal]

Hey guys, I came across a J head, a bit more expensive, but chromed ways which look really nice, ect. ect. I'll probably go look at it this weekend

However, all these levers, knobs, ect. on the J head are a little concerning as /anything/ could be broken behind them and I'm not sure I'd know, is there a quick and dirty on what all of these things do?

 

[sd624]

If you could start it up that would would be helpful. Just listening can tell a lot. Check out the taper on the spindle. Stick your finger up in the spindle and feel for any scoring then check for the key that engages the collet. If all feels good get a magnetic base dial indicator and set it up to measure the inside of the spindle right on the taper. Rotate the spindle by hand. Any reading over ~.0004 my be a issue with the spindle bearings or damage. Replacing the bearings and regrinding the taper will cost between 500 and 600 bucks so keep that in mind.

Next if it has Zerks make sure someone didn't actually use grease. It happens a lot because Zerks are for grease right well not on a BP. Using grease instead of way oil will prematurely wear out the machine. Not only does it not get to all the spots that need lube it holds the chips and grinds them into the ways.

Take a close look at the ways on the knee and under the table.

If theres a lot more wear in the center of the knee then the ends. If you adjusted the gib to take all the movement out of the saddle you couldn't move the saddle to the ends of its travle. Very common problem and would have to be ground, scrapped, and flaked if you can't live with it.



Check the backlash in the X and Y lead screws in the center of the table and the knee and then run them to the outer limits. If there's than .005 difference the screw is wore in the center and my need to be replaced. If you plan on running a DRO then the backlash doesn't matter.

Heres some other checks you should do.

1. Does it shift in and out of back gear easy

2. Does the quill move up and down manually without dragging or binding

3. Does the head tilt in all 3 directions

4. Does the quill operate in power feed in both direction and all 3 speeds

5. Does the power feed auto stops work in both up and down feed

The nice thing with BPs every part is available. A simple google search for Bridgeport parts will return several sources. Ebay also has tons of parts.

 

[Metal]

Thanks SD!

one question... what would you even use a reverse power feed for in the quill?

 

[sd624]

That's a good question Metal. I only recall using it once many years ago while I was boring a cylinder but can't remember why. The test is to check and see if the trip ball lever is broke. If the auto stops don't work or don't work in one direction then it's probably broke. It's an easy fix though.