# Let's Talk About Wear On Our Bridgeport Milling Machines



## Janderso (Jun 18, 2018)

Hi,
I am new to milling. I purchased my 1970 Step Pulley last winter. I really had no idea what to look for and the price was right so I bought it.
As I am learning about this machine and getting to use it more and more, I am finding a few things that concern me.
First of all, the Y and X tighten up on both ends. I find there is table movement (I haven't measured it yet). When I am in the highly used zone and enjoying free wheeling of the ball cranks there is quite a bit of table movement. As I move from side to side the movement is significantly less as the ball cranks tighten up against the gib.
I tighten up what I can when milling and so far the machine has performed well for me. When I make a cut, I check for squareness and depth consistency and I find little deviation and I am cutting right angles.
Now, maybe for this hobbyist the wear has not yet become an issue.
The head is quiet, the quill binds a bit but that's OK, the back gears are quiet and all the machine functions seem to work OK.
I have a hunch there are many of us in the same position. 
What are you doing about the wear? When I tighten up the locking screw the table tightens up great. 
Have you considered having yours ground/scraped in?
Have you considered doing it yourself? Cringe.
What options are available?
I'd like to talk about it.
Jeff


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## markba633csi (Jun 18, 2018)

Yes it can be scraped in but it's a job. Maybe Rich King can elaborate on this, he's our resident expert
Do you have a long table version or a short one like 32"?  Shorter the table the less work to fix I think.
Sometimes the gib can be shimmed to give some improvement


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## Technical Ted (Jun 18, 2018)

Here are my feelings on this subject for what they are worth. Unless you are either very lucky or spend more money than I could justify for my use, you will most likely end up with machines that are either older, have more wear or both...

My 2J Bridgeport has wear in the Y travel and I ended up putting a shim behind the gib. This helped quite a bit and I have it adjusted so it travels the whole distance, but does get tighter on the ends. I have not measured slop in the center of travel with an indicator, but have not had any issues on any of the jobs I have done on it, so it probably depends a lot on the type of work you're going to do on it. For my use, a hobbyist, mine is fine and if I do see an issue I can use my Jet mill which is like new and very tight (but I don't really see this happening).

I don't have the knowledge or equipment to scrap the ways in. My feeling is if it's not broken (for my use) don't fix it.

You said the quill binds. Does it bind near the top? If so, try loosening the set screw on the very bottom collar of the quill (in the back). I had to do this and it freed mine up fine.

Ted


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## Janderso (Jun 18, 2018)

markba633csi said:


> Yes it can be scraped in but it's a job. Maybe Rich King can elaborate on this, he's our resident expert
> Do you have a long table version or a short one like 32"?  Shorter the table the less work to fix I think.
> Sometimes the gib can be shimmed to give some improvement



It's a 42" table.
I would like to shim the gib. If I could take up the wear in the center only.
I am thinking you would loosen the gib to allow free table movement, then determine the amount of shim required?
How would you go about that? Trial and error, or is there a more scientific method?
Ted, I'll check the set screw, thanks.


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## Technical Ted (Jun 18, 2018)

Is the front end of the gib (inside, smallest end) extending beyond the saddle and sticking out some? It shouldn't be. When I did it to mine, I tried getting the gib in about the center of it's intended position, leaning towards more towards the front of the machine where the adjustment screw is rather than in farther). I removed the gib and cut a shim to fit behind it and if I remember correctly cut the shim a little long on both ends so I could bend some at 90 degrees to help hold it in position. I planned on just using trial and error, but I hit it on the first try. Hopefully, you can get away with 0.005 - 0.010". You will also need to make holes where the oil grooves and holes are. I used a Dremel to do this and it worked well.

Now, I'm no expert here, but this is what I did and it seems to be working well.

Edit: It didn't seem like the collar set screw on the quill being too tight could possibly be causing an issue, but it doesn't take much to make the quill out of round because of the close fit. I loosened the screw and just barely snugged it and it works nice and free now where prior to doing so made it bind quite a bit. 

Ted


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## Cadillac (Jun 18, 2018)

What you want to do is first see if the gib has adjustment? Sounds like it’s worn if it’s tight on the ends of travel then nice and free in the center. Also check the dovetails underneath. They may be rusty or have debris on them causing it to be tight. Recommend pulling the gibbs and at least clean and inspect. Gives you a opportunity to oil and adjust to see where your at? Shimming is only necessary if gib has no more adjustment. And that still won’t take care of the hour glass shape in the ways probably.


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## Janderso (Jun 18, 2018)

Technical Ted said:


> Is the front end of the gib (inside, smallest end) extending beyond the saddle and sticking out some? It shouldn't be. When I did it to mine, I tried getting the gib in about the center of it's intended position, leaning towards more towards the front of the machine where the adjustment screw is rather than in farther). I removed the gib and cut a shim to fit behind it and if I remember correctly cut the shim a little long on both ends so I could bend some at 90 degrees to help hold it in position. I planned on just using trial and error, but I hit it on the first try. Hopefully, you can get away with 0.005 - 0.010". You will also need to make holes where the oil grooves and holes are. I used a Dremel to do this and it worked well.
> 
> Now, I'm no expert here, but this is what I did and it seems to be working well.
> 
> ...



I just found the video that H&W made about this same subject. Unfortunately it won’t solve my problem, I still have gib adjustment available.


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## Janderso (Jun 18, 2018)

Cadillac said:


> What you want to do is first see if the gib has adjustment? Sounds like it’s worn if it’s tight on the ends of travel then nice and free in the center. Also check the dovetails underneath. They may be rusty or have debris on them causing it to be tight. Recommend pulling the gibbs and at least clean and inspect. Gives you a opportunity to oil and adjust to see where your at? Shimming is only necessary if gib has no more adjustment. And that still won’t take care of the hour glass shape in the ways probably.



I should take the table off and check for items you mentioned. It couldn’t hurt.


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## projectnut (Jun 18, 2018)

With a machine of that age there is likely a fair amount of wear on the lead screws and nuts.  A good deal of the play at the center of the travel can be eliminated by either cutting or replacing the brass nuts.  If it has the original nut on the X feed it is split about half way through in the middle something like this:

https://www.mscdirect.com/browse/tn...MIhJWj_4De2wIVAxBpCh2REgR7EAYYASABEgIFKPD_BwE

You can finish the cut, square the ends and reinstall them to eliminate a vast majority of the slop.  Once that's done you can adjust the gib to eliminate even more.  My 1972 machine had  considerable slop in both the X and Y directions when I first got it.  I cut the nuts, readjusted the gibs, and got the play down to .005" on the X axis and .007" on the Y axis.  I've had the machine going on 20 years and both axis have about .010" play today.

I would contact these people for parts and advise on how to proceed:

https://www.mscdirect.com/browse/tn...MIhJWj_4De2wIVAxBpCh2REgR7EAYYASABEgIFKPD_BwE

They are extremely knowledgeable, their prices are more than fair, and they are more than happy to help out.  I have done business with them since I first purchased my mill.


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## Janderso (Jun 18, 2018)

That gives me hope Mr. Projectnut. I really do not want to get too carried away with my old mill and I do love the old Iron.
MSDirect and I are already acquainted $$$$$ 
Thank you.


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## Technical Ted (Jun 18, 2018)

I assumed you were asking about the ways, not the lead screws and nuts correct? Maybe I misunderstood. Backlash in the lead screws/nuts is a totally different story.

Sorry if I was on the wrong track,
Ted


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## cjtoombs (Jun 18, 2018)

The problem on a worn machine with adusting the gibs, as you have stated in your initial post, is that the wear is not even.  You can adjust, shim, or whatever you want to on the end of the table and it will still be loose in the middle by the amount of wear on the table.  I have not scraped in a machine myself, but I have taken Richards scraping class and have ammassed most of the equipment I need to scrape one and have plans to scrape a couple of my machines.  The problem with scraping a machine in from my viewpoint is the aquisition of all the things you will need to do it.  Straightedges run about $10 an inch, and to scrape a 42" table, you need a wedge straightedge (which are harder to find than a flat one) to do it.  So that's $400+ for a single straightedge.  You can make a hand scraper yourself, but that's more time.  A Biax power scraper will run you about $700, new blades are about $100 each.  Richards scraping class was $600 when I took it, some years ago.  You need a surface plate large enough to check a 42"+ straightedge on so figure on a 36" x 48" surface plate.  Depending on where you buy it and what grade, that's about $500.  So my take is, unless you have a one of a kind machine or you really want to learn how to rebuild machinery, use it as is if it's doing what you need it to do, otherwise buy a better machine then sell the one with the wear.


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## Janderso (Jun 18, 2018)

cjtoombs said:


> The problem on a worn machine with adusting the gibs, as you have stated in your initial post, is that the wear is not even.  You can adjust, shim, or whatever you want to on the end of the table and it will still be loose in the middle by the amount of wear on the table.  I have not scraped in a machine myself, but I have taken Richards scraping class and have ammassed most of the equipment I need to scrape one and have plans to scrape a couple of my machines.  The problem with scraping a machine in from my viewpoint is the aquisition of all the things you will need to do it.  Straightedges run about $10 an inch, and to scrape a 42" table, you need a wedge straightedge (which are harder to find than a flat one) to do it.  So that's $400+ for a single straightedge.  You can make a hand scraper yourself, but that's more time.  A Biax power scraper will run you about $700, new blades are about $100 each.  Richards scraping class was $600 when I took it, some years ago.  You need a surface plate large enough to check a 42"+ straightedge on so figure on a 36" x 48" surface plate.  Depending on where you buy it and what grade, that's about $500.  So my take is, unless you have a one of a kind machine or you really want to learn how to rebuild machinery, use it as is if it's doing what you need it to do, otherwise buy a better machine then sell the one with the wear.



I appreciate every word of your post. You have explained the process and expense of the home repair very well. It takes experience, equipment and training to properly repair these old machines. As Mr. King has said in one of his posts, (the discussion was relating to one of the Acer Knee Mills) you can't rebuild a Bridgeport for what you can buy a new machine for.
I would love to take one of Richard King's Scraping classes. I am still working, my wife expects me to include her when I have time off. With only 3 weeks a year off, it's difficult to schedule.
I am going to learn and use this old beauty as long as I can. Then I will look at options.
As I said in my post, even with the table slop, It has done everything I have asked of her. (so far anyway)


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## Janderso (Jun 18, 2018)

Technical Ted said:


> I assumed you were asking about the ways, not the lead screws and nuts correct? Maybe I misunderstood. Backlash in the lead screws/nuts is a totally different story.
> 
> Sorry if I was on the wrong track,
> Ted


Actually Ted, The backlash is not bad, somebody must have already tightened up the brass before I got this mill. I have seen the videos you speak of though. It doesn't look too tough.


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## chips&more (Jun 18, 2018)

As it wears that is the nature of the beast. It’s VERY NORMAL to have the wear you are noticing. You said it still makes good parts, so use it and enjoy. Scraping is another world. You can replace the feed screws and nuts. That would help A LOT, but you would still have the tight ends on table travel. Things you should ask yourself. What is my work envelope? How many hours a day do I use the mill? What are my tolerance parameters on the parts I make? etc…etc…etc


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## Janderso (Jun 18, 2018)

Good advice


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## Boxster9 (Jun 19, 2018)

I wish I had taken Richard King'a five day class for $600.  Last month, when I took his informative and extensive class was $1,650.  Not cheap but well worth the effort.


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## Richard King 2 (Jun 19, 2018)

I have a couple suggestions if you are short of money.  First checking the size of the shim is easy.   Take out the gib and clean it and run a wire into the gap the gib was in and wrap the wire around a rag and pull it trough there with some solvent on it to clean out the hole if it is dirty.  Then whit is clean stone or smooth cut file the ends of the gibs and slide the gib in so the slot that the gib screw  fits in and with the bigger round flange is about 1/2 way into the.  Then take a feeler gage and check what the opening is.

Depending on how much the gap is, you could shim the back side of epoxy on some Rulon 142 to the gib or on the back side of the saddle.  Rulon is self lubricating plus it compresses a little, so it will compress on the tight ends and turn easier Your table is bent too, convex probably .005 to .010".  The convex of the table can also make the ends get tight plus wear.  I have some orders I need to get out.  I'll come back later.  Rich


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## Janderso (Jun 19, 2018)

Thank you Mr. King.
I'll be assessing the gibs this weekend. Your opinions, ideas are greatly appreciated!!
Jeff


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## dlane (Jun 19, 2018)

My mill (supermax) is a little tight on the ends of travel, I figure if I use it on the ends eventually it will wear in and be the same as the middle of table.
My vise is at the right side of table now , in a couple months I’ll put it on the left side and alternate until it’s the same as the middle I almost never use the full travel of the table . My thinking it will fix itself eventually  .


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## Janderso (Jun 19, 2018)

I have often thought of moving the vise to one side or the other but visually I could never sleep.
A bit OCD.


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## dlane (Jun 19, 2018)

With the vise on one side I have room for the RT or tilting angle vise on the other side, I’m trying to wear the ends the same as middle, another 40 yrs just like new,


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## Janderso (Jun 19, 2018)

Richard King 2 said:


> I have a couple suggestions if you are short of money.  First checking the size of the shim is easy.   Take out the gib and clean it and run a wire into the gap the gib was in and wrap the wire around a rag and pull it trough there with some solvent on it to clean out the hole if it is dirty.  Then whit is clean stone or smooth cut file the ends of the gibs and slide the gib in so the slot that the gib screw  fits in and with the bigger round flange is about 1/2 way into the.  Then take a feeler gage and check what the opening is.
> 
> Depending on how much the gap is, you could shim the back side of epoxy on some Rulon 142 to the gib or on the back side of the saddle.  Rulon is self lubricating plus it compresses a little, so it will compress on the tight ends and turn easier Your table is bent too, convex probably .005 to .010".  The convex of the table can also make the ends get tight plus wear.  I have some orders I need to get out.  I'll come back later.  Rich



 Richard/Mr. King.
It's not a matter of "short on money", it's a matter of justifying the expense.
 I would really need to cherish my old Bridgeport to have it professionally scraped in. Freight and scraping the table, saddle and knee would have to run in excess of $5,000 right?


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## Richard King 2 (Jun 19, 2018)

If your only having an issue with the table you could get it ground .  I just did a 3 classes in the bay area and was told there is a grinding company in near by that grinds tables.  Also there is a grind shop about 1/2 way between SF and LA.  That one is schaffergrinding.com  

 I will have to email the students about the name of the other place.   You could send them the Saddle and Table and if your Machine is not chrome plated I think I could talk - write through it .  Fitting it.  Plus  Member Benchee  (John York) is a good scraper and lives near Napa.  He has all the scraping tool you would need.   He could show you how.  There is always a way to skin a cat, just have to have the guts and an open mind.

Another one in CA  http://www.qualitygrinding.net/


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## Kroll (Jun 24, 2018)

Give you an ideal, take a look at Youtube and search.Will give you an ideal of what is involved having a table done.I had no ideal till watch several Youtubes and scraping.It can get very expensive if this is a hobby


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## Richard King 2 (Jun 24, 2018)

Yes and no.  depends on what your going to do.  As for Preventative maintenance and small touch up's it can be less the $100.00.  If your going to do some hobby work probaly cost you $1000.00 for a plate, tools, supplies, some dvd's, a book or 2.
keep an eye on Ebay and Craigslist to find deals....etc.

Do all the test with your own tools, take a scraping class,  should be able to rebuild your own machines if you take it slow and ask question on here and the few of us who know can help you. $4000.00 to more....depending on you buy new.   You wi;; also have to spend money if the parts need to be replaced or renewed at so,e pother shop like your table.   Most figure you can rebuild for 1/2 to 3/4 the price of new.


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