Let's Talk About Wear On Our Bridgeport Milling Machines

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
 
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.
 
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.
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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)
 
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
Click to expand...
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.
 
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
 
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.
 
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
 
Thank you Mr. King.
I'll be assessing the gibs this weekend. Your opinions, ideas are greatly appreciated!!
Jeff
 
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 :rolleyes: .
 
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