# 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.


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## 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!


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## Metal

Thanks Bob, good to know!


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## 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


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## brino

Metal said:


> 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 





Metal said:


> "not good" condition


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



Metal said:


> 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


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## 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.


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## 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?


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## 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.


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## Metal

Thanks SD!

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


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## 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.


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## Metal

Yeah, for the life of me I cant imagine why you would want to feed upwards, maybe some kind of funky upwards slot cutting or something>

One last question: is there any real physical difference between the 1 -> 3 hp bridgeports?  eg: if I need to could I get a higher power motor for this without having to replace a large portion of it?


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## fast freddie

the round ram BP is plenty rigid enough, I ran a m head many years ago and it took # 7 B&S collects (1/2 inch shank capacity).  that machine will do most things and you can keep you eye out for a j head


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## sd624

Metal said:


> One last question: is there any real physical difference between the 1 -> 3 hp bridgeports?  eg: if I need to could I get a higher power motor for this without having to replace a large portion of it?




Typically your 1hp is going to be a step pulley and the 1.5 to 3 hp will be vari speed. But I've seen all three on each.


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## Metal

Checked it out, as far as I can tell it looked pretty good
Everything functions as expected
Backlash is roughly 40 thou in x, 35thou in y and consistent as far as I could tell, so it might be the ballnut, but its not enough that I really think its an issue.
There is more resistance in the Y axis near the edges of its travel, for the last perhaps 2 inches, but not "binding" up, and the mill was nearly bone dry and resistance was still not very much at all.

soooo.. might be buying it, none of this is concerning me much for my uses (mostly 6061 aluminium)


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## sd624

Did you take any pics?


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## Metal




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## Metal

Well I bought it 

Anyone have any ideas on unloading it off a truck with a forklift since it won't be on a pallet (top heavy, I know)
I've seen pictures of backing the ram up, putting wood on forklift forks and lifting the mill by both sides of the ram, but it seems like its center of gravity would be farther forward than that and would make that really dicey


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## JimDawson

Here is a couple of different ways that I do it.

Wood on the forks method,  I have moved a lot of mills this way.  I normally use a 2x4 under the back, and 4x4 under the front.  This helps compensate for the front heavy condition.  This particular mill is about 3500#, your BP is about 2500#  8500# reach fork lift




Lifting straps under the ram.  Doubled up cardboard under the ram to protect the straps.  Also a 2x4 under the ram on the front strap to adjust the length to balance the load.  These are 6000# straps, 12,000# in this configuration.  5000# forklift.





A drop deck trailer makes for easy unloading.  We just pulled it off the trailer with a come-a-long.


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## Metal

Unloaded and ready to be disassembled!

Looks like the easiest way of doing it due to the power feed is removing the table at the y axis saddle, going to give disassembly and move a shot on saturday!


2 questions!:

1. how paranoid should I be about snapping off any of these levers on the J head when removing it? it realy doesn't seem like there's a good way of supporting the front of it when removing it (with straps)

2. how do I not kill myself while removing the knee, I'm guessing once the saddle is off I wrap straps aroundeither side and "hope" to balance it that way?, the curved surface with no good way of gripping it is a head scratcher.


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## JimDawson

What lifting equipment do you have available?  I have normally disassembled/assembled the head in place.  The last thing you do is remove the tilt bolts and pull the rest of the head, it's about 50# without the quill.  If you have overhead lifting equipment, you could choker the head between the motor and the head to support it and then pull it off.

I would normally pull the table off, then the saddle.  The power feed is not too hard to remove.

I have never pulled the knee, but there is some space between the knee and the column, you might be able to get a strap around it that way.  Maybe other can help out there.  I might be tempted to leave the saddle on and get straps around that to lift the assembly.


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## Metal

Where it is now we have a forklift, but where it is going I'll be using an engine hoist, I'm going to do some minor disassembly to check things out and grease, but first order of business is getting it out of the warehouse where I had it delivered, which means breaking it down into some of the larger components (really just the table and head I think should do it)


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## JimDawson

A fork lift makes life easy.  

The head breaks down into three major components; the motor and housing, the back gear assembly, and the actual head.  Each one can be manhandled into place for reassembly.  The reason I say this is getting the assembled head back in place with an engine hoist might be a problem if you don't have some way of increasing the lift height.

The table can be put back on by setting it on a table and adjusting the height with the knee, it just slides back into place.  One note:  Remove the gib before removing the table, and put the gib back in after the table is back in place.


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## Metal

I fully expect to take the head apart on my workbench and inspect/clean/lube it, there's just too much stuff going on inside of it to not give it a once over, Ive seen on youtube a guy made a spindle mount that attaches to the table, then he uses the table controls to remove/replace the head, which is pretty slick, which I may consider for putting it back together!


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## JimDawson

Metal said:


> Ive seen on youtube a guy made a spindle mount that attaches to the table



Now that's a cool idea that I never thought of!


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## Metal

give me a few i'll track it down!

here we go, pretty clever guy, its just a plate with a reinforced "collet" on it


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## sd624

Removing the knee is the easy part. You put bar down in the center by the second rib. Use some c clamps to keep in in place. Put your lifting strap around the bar and lift knee off.


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## JimDawson

Metal said:


> give me a few i'll track it down!
> 
> here we go, pretty clever guy, its just a plate with a reinforced "collet" on it



That is very cool, I'm going to have to build one of those next time I need to pull a head.  Thanks for posting!


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## Metal

So! started disassembling and moving, everything is going well. and we're down to the ram and column!




Some questions
1: It appears this guy either used grease or the oil became black and thick, I was planning on pumping up a weed sprayer and spraying way oil through it to verify all the paths are clear, a lot of hand degreasing in my future.

2. I need the sizes of the threads of the zerk fittings, since its apart it'll be easier to 1 shot lube it now while I assemble it, anyone know?

3.  leadscrew nuts are actually... unbelievably cheap on ebay (~45 per axis, what? I was expecting hundreds)  is there a reason I shouldn't just replace these as I'm reassembling? I'm not sure how to measure wear on a the leadscrew, but it "looks" perfect.

4. as above, I'm not sure how to check if a gib is worn, they look fine to me, if caked with grease


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## brino

For any small oil channels I'd be tempted to use a solvent first to remove as much of the dry grease as possible. Once that washes thru, then start feed copious amounts of the recommended lubricant thru. It's easier on the gibs where you can scrape most of it off once they're out.

With solvents use appropriate protection; ventilation and eye-shield......it's amazing how much even a manual wire brush can throw at you. Also for flammable solvents be careful of any flame or spark (heaters, motors, a powered wire brush can also spark......)

-brino


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## Metal

Yeah, my previous mill (benchmaster) was in the same condition, but was only a 500 or so pound mill, so refurbing isn't super new to me, it'll be all wire brush and welders mask next weekend


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## Metal

One more: I'm poking around for a VFD, but am not really sure what I should be looking for feature wise.

Eventually the VFD will be controlled by mach3, right now being able to control it through the keypad extension (which ive seen on a few) would be ideal.  at the same time i'm running ~1hp, I may increase this, poking around I'm finding /serious/ deals on ebay, but figure there's a reason that these particular VFD's are so much cheaper.

Alternatively, ive googled around for just replacing the motor with a brushless DC motor, which seems perfectly doable and kills both birds with one stone since I'd get an oversized high power motor/and control in one go, but it doesn't seem many (any?) one has taken the leap on a mill this large.


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## Metal

cleaned up the saddle, and half of the knee!  I'm thinking of repainting, I really liked a yellow bridgeport I saw, but don't want to go through all the effort of stripping, sandblasting, and repainting, hrm.

A plain old ziptie made short work of the clogged grease fittings paths, then flossing them with paracord soaked in degreaser.


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