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Options for worn ways repair

Discussion in 'MACHINE RESTORATION & WAY SCRAPING' started by jmhoying, Oct 13, 2013.

  1. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    My newly purchased 1979 Millport (Bridgeport J-head clone) has a lot of slop in the table. I've tightened the gibs but still get a fair amount of rotating on the center line motion when pushing or pulling crossways on the end of the table. I can make the problem disappear by tightening the x and y locks. Like most mills that are well used, the problem is most noticeable in the central area of movement.
    I guess I already know that the answer to my question is "complete scraping job", but I was wondering if there is a method that will tighten up the table without all the investment in specialty tools and the learning curve for scraping. I know that is the only way to bring my Millport (Bridgeport J-head clone) back to new standards is scraping, but at this time, I don't have to have 100% precision in the ways. I haven't checked them for wear, but would there be any benefit to truing up the gibs only at this time?

    Thanks,
    Jack
    Fort Loramie, Ohio
     
  2. Richard King

    Richard King Active Member Active Member

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    Most of the time the top of the knee is the worst as the ways are shorter then the table and smaller wears faster. If you want to check the knee for a quickie cheap appraisal,get a couple of 5/8 dowel pins or some drill rod (if you have to you could use cold roll, but mic it and mark with Sharpy a 3:00 and 9:00 side and always use the same way, will explain how next) about 2" long. Crank the saddle out as far as you can with gib loose toward the back. Clean and stone the ways to knock off any burrs. Then lay one pine on each side of the top of the front of the knee opposite each other and use a micrometer to measure the distance from out side of pins and record.

    Then push the pins in toward saddle say 3" and measure again, and again. Then crank the saddle to the front and clean and measure the other side or behind the knee. If you don't have 8 to 9 mic I think that's the size use a dial caliber. The table is probably bent and worn. Many rebuilders will cut the T-Slots to relieve the peen-ing or stretching the metal in the T-Slots. I have never done this, but believe it can be an issue. I have turned a table over one time and peened the bottom of the table in the middle area with a rounded punch and have straightened them. I have seen some Bridgeport's table bent .012" The bent table will make it bind up on the ends. Take the table off to check it and I am hesitant to tell you to peen it if you don't have the plate to lay the table of to check it. I suppose you could use a 36" steel rule or a straight sheered piece of sheet metal and use a feeler gage to judge the table top. I would just lay a camel back up there, but I have several sizes. Measue the knee and table and let me know. To see if we can make a few suggestions. Rich
     
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  3. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    Richard,
    Thanks very much for your detailed response. I measured the ways on the top of the knee tonight and it looks like the center area is about .011 smaller than the front and back. Is this considered a bad case?
    Jack
     
  4. Richard King

    Richard King Active Member Active Member

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    Its terrible. Probably a combination of the flats being lower allowing the pin to roll deeper into the dovetail and the dovetail is worn too. If you have a surface gage like a Starrett (56a) and attach a dial indicator on the rod swivel and measure the flat of the way to the top clearance or the surface on top of the dovetail. C to A and B to C Do the test along the the flat the same as you did with the pins. I hope my crude sketch of the top of the knee works.
    ............a..................... b .............
    _____\------i_______i-------/______
    __c __\............................/__c____
    l..................................................l

    there isn't an easy fix. It will need to be machined and scraped or scraped. It's late will write more later. Have the Uncles funeral tomorrow. So will probably not write till Friday. Rich
     
  5. bkcorwin

    bkcorwin United States Active User Active Member

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    A few questions on how one would interpret these results if you don't mind.

    What sort tolerances would one expect of a new machine? Would these measurements be dead on?

    If .011 is terrible, what sort of measurement would be acceptable? I know acceptable depends on the tolerances one is trying to work to, but could we get some kind of ballpark region of "not too bad"?

    Thanks much
    brian
     
  6. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    I've scraped in .011" plus thousands on a old knee slide on a ancient Brown & Sharpe mill in my younger years. Used a cast iron surface plate that must have weighted 150 lbs. It wasn't easy. At least at the time, we had a Biax scraper that helped. Dad and I took turns scraping, finally got it to about 70-80% over most of the areas. There were hard spots in the cast iron from all the years of pounding from the saddle. After that ordeal, the saddle was put up on a shaper a planed. Talked about a lesson learned!!!!

    Not to speak in Richards place, you ask, What is considered acceptable".

    I my words anything is acceptable if it is doing a satisfactory job in the work expected from the machine. If it's not, then its time to evaluate and determine what the cause is. If it is wear, as indicated, how much? Next, put a game plan together on how to correct/improve the wear to when the machine is put back in operation it will do satisfactory work.

    Does not mean the wear in the slides has to be perfect within 50 millionths in flatness as Richard is known to teach and do. (No offense Richard) I bet for most of us HSM, if It was within .002-.003" in flatness (in 12"?), it's good enough to last a lifetime for us. My 13" lathe has about .004" wear in the bed ways, but I can keep the taper in 18" to within .0015", which tickles the heck out of me, closer if I baby it.

    I will say .011" is a bit much to live with or to fix by scraping.
     
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  7. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    I measured the distance (a-c and b-c). Both are right at .003 lower in the center. There are a few faint scrap marks on the front and back edges of the flats.

    I assume that one of the "scraped" in the last sentence was supposed to read scrapped, which is scary to me. The part that really upsets me is that when I called the Craigslist seller, it turned out to be a classmate of my daughter, so I thought I could believe him when I said that I definitely didn't want a worn out mill. To be fair, I think he was sort of a hack machinist who didn't know any better (which puts a lot of the blame on me for not investigating better). The unit wasn't powered up, so I didn't start noticing problems until I got it home. An expensive lesson learned, that's for sure. That being said, I had contacted the seller early on when I found other issues (gear on power x feed, brake shoes, etc) and he gave me some of the purchase price back to buy parts. Now, I'd sell it back to him at a loss just to wash my hand of it.

    I have to agree with Ken's comment about not needing this to be "better than factory" perfect. I'm mainly using it for repair parts and such, but it still needs to be better than it is now.

    Jack
     
  8. astjp2

    astjp2 United States Active User Active Member

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    Get them straight and aligned by scraping, then use turcite to make up what was removed...Tim
     
  9. savarin

    savarin Active User H-M Supporter-Premium

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    I have no experience in this but have read somewhere that a product called "Moglice" was developed for this sort of problem.
    Anyone have any experience of this product?
     
  10. Richard King

    Richard King Active Member Active Member

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    Lets re-evaluate what we have read so far: It would HELP if we all had some photo's to look at, so we are not guessing. I am trying to help him figure out what to do as a professional point of view. I tell my students when I am rebuilding a machine and I find ways out more then .005" to get them machined as scraping off .011 and keep it square, parallel, flat, and the right amount of points when done take a lot of work and in my case, a ton of time. As a pro, time is money because I have no doubt quoted the machine before getting the job. You owners who have lots of time can spend 100's of hours and time is not money if it's a hobby. On average on all the Bridgeport or clones I average 40 to 60 hours for the rebuild of the ways including the column, knee, saddle and fitting a reground table to the saddle, all the gibs. The machine spec's are better then new at .0002" per foot and 20 PPI. (I would never scrape a Knee Milling machine to .00005") I get the table reground and this does not include rebuilding the head.
    To understand what he has I had him measure the machine. It's difficult to help over the internet but this will take a while. Rich in the UK, we spent weeks getting him on track, not 2 posts. Jack you have to be patient and the others lets analyze everything before getting to excited please.

    I had Jack measure the ways so I could give him professional advise as I have probably re-scraped over 400 + Bridgeport's in my 40+ years of re-scraping Bridgeport's. My brother and I would have contests on who could scrape one the fastest.

    I first asked Jack to measure the using the dowel pin's then the surface gage. To me .011 is terrible but can be repaired. The double "scraped" was a typo this morning as I was under the gun to get to the church, but wanted to help you. You need to relax and let us help you figure this out before calling the former owner. I have seen machines with deep scores, worn .020 and the owner says it worked great as he was using it more for a drill press then a mill. If you look back in this forums past posts. You will see some imported new machines that were sold new and were off .012" Now that's terrible too.

    You don't tell us what you paid for the machine, so we can't judge your price and the machine value. Last spring LQQQ, I apologize if I botched the name, but he bought a machine that had cardboard behind his gibs, the knee, column and head stock were from different machines. He as far as I know fixed his machine. His machine was a mess and also terrible.

    OK lets get to helping him on his machine.

    Next thing I would like you to do is to remove the rear saddle wiper and see if the gib can be moved back future. Many times the gib hits the aluminum wiper plate and it appears like it is out of adjustment. Next you have to tell me or us what your expecting from the machine when your done? Can you live with .002" slop in the gib clearance. Have you also checked your table? Is it sloppy too?

    In order to scrape the knee you are going to have to buy some tools, a straight edge a hand scraper, a precision blade square, bluing, etc. Probably a minimum of $500.00 in tools if you are lucky to find good used ones. and probably $1000.00 to $2500.00 or more if you have to make or buy newer ones.. If you have more machines to rebuild in the future then the investment would be worth it. If not you may look for a local rebuilder to do the work for you.

    If you need help posting some pictures call me and I can help. If you don't have a digital camera and cant afford one, take some regular pic's and mail them to me. Those digital camera's are really amazing and if you don't have one you can buy them reconditioned or new for cheap online. PM me or call me and i'll help you.

    I will be at home tomorrow and if you want to call me, please do so. 651 338 8141. It is so much easier to understand from a phone call. Then we can write here so we keep everyone in the loop. Rich

    I added some info to his first post.

    - - - Updated - - -

    I used to be a Moglice Rep and have used it many times. You need to have a precision surface to mold the Moglice to. His ways are worn and Moglice is used where Turcite / Rulon would ride against the scraped way. Moglice has a product called Score Ex, but would not be used in this area.
     
    Last edited by a moderator: Oct 18, 2013
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  11. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    Richard,
    Thanks again for your help. In the end, I want a machine that I can trust to be fairly precise. Not planning on making any replacement parts for Boeing, but I can't live with the slop I have now either. A 75% improvement would be great.
    I located the table in the mid position of x and y this morning and did a few measurement to explain the slop I have. (this is with the gibs as tight as I can adjust them) With a dial indicator on the end of the table, I can pull and push the end of the table .040" (horizontally, front to back). If I lock x and y, it's around .002" movement. If I only lock the y, the table has about .009 of movement. If I move the table to the front of the knee, and lock the x, there is about .005 movement.
    Concerning the knee gib. When I was trying to figure this out on my own a few weeks ago, I had noticed that the gib was pushing the rear wiper out of position. My solution was to shorted the gib by 1/4", but of course, this didn't help my situation. I also had suspicion that the gib tightening bolt was bottoming out and not pulling the gib tightly, so I removed 1/8" from it, which didn't help either. Sure seems like no matter how tight I can turn the adjusting screw, it's not pulling the gib as tight as it should.

    I paid $1700 for the machine, and got a few accessories with it.

    Here are a few photos that I took this morning. I probably have double the expense in camera equipment than I do in my mill and lathe, and the camera hobby is what I use to pay for the metalworking equipment. (for some reason, by wife doesn't think I need another hobby???) If you want any photos of other locations, let me know.

    port01.jpg
    port02.jpg
    port03.jpg
    port04.jpg

    P.S. The hand-wheels were purchased from an EBay seller and were the best thing I added to the mill (so far).

    Jack
    Fort Loramie, Ohio

    port01.jpg port02.jpg port03.jpg port04.jpg
     
  12. Richard King

    Richard King Active Member Active Member

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    As I was about to hit submit Jack called me. I will add this and then let him explain what he did this morning.


    That really helps with the pic's I mentioned the help with the camera as many of the new members need help and are afraid to ask. I can see you could teach me a thing of two about taking pic's. When you check the gibs be sure to month the mag base on the knee and put the indicator on the saddle and put the mag base on the saddle to measure the table. I can see 2 fixes now. one will "patch it up" and no scraping will be needed and that is to glue some Rulon 142 to the riding side of the gibs and that will make the gibs fit better. Or scrape the ways and do it right. The ways look pretty bad (terrible) and need to be rescraped. The Rulon will compress a bit as it is moved to the tight ends, but you will no doubt still have the .003 to .005" slop. The ways have small scores in the and I would guess they are another .005" deep. You could install the gibs to where they would be when new. The thick end even with the back end and so the wiper plate will fit. You can use a feeler gage and see how much shim you will need to know what size Rulon to order.

    You could take apart the machine and send the knee, table and saddle, gibs to a rebuilder and I would guess it would cost you $1500.00 to $2000.00 to get it rescraped. You would do all the dismantling and assembly. You could probably do it and if there happened to be a member close that had the tools and expertise he might help. Their is a guy who comes to the forum named Sidecar who specializes in Bridgeports and it might me worth while asking him for a quote. That's a major repair and I am sure you could do it, but never scraping and not having the correct tools, your looking at a BIG job. Is there any members close to him with the tools and expertise who can help him?
    A thought just came to me. High Quality Tools is in Ohio who sell Millport parts and they may have a local rebuilder who might give you a deal if you do the mechanical work and all he does the scraping. I know some of the members might suggest you file and scrape the the ways to get them better, but as an instructor and pro i would never suggest you do that. What do you want to try? Rich
     
  13. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    Before I called Rich this morning, I thought about the fact that there is a machine rebuilding business about 1/8 mile down the road from me. I've never been in the place, but stopped in to see about getting my table fixed up. He is going to get back to me with a price. I'm hoping that I don't get extreme sticker shock, but I do realize that repairing it requires a lot of time. I'll let everyone know once I get the estimate. The company is http://edwardsmachine.net . I got a tour of the place (maybe 5 employees) and it was neat to see all the pretty scraped pieces laying around. Once I get a price, I'll have to decide what avenue I'll go down.

    Update: I didn't hear back from the company today with an estimate, so it'll be next week sometime until I get it.

    Jack
     
    Last edited: Oct 18, 2013
  14. There is no cheap, easy fix. Scraping is time consuming, hard work. Many rebuilders will not accept a job to do a 75% fix, as their reputation is based on precision. Good luck on your project.

    John Fahnestock
     
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  15. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    John,
    I understand those statements completely. We'll see what the estimate is.

    Maybe I'll end up just takinga disc grinder to it! ;-):dunno:

    Jack
     
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  16. astjp2

    astjp2 United States Active User Active Member

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    Blasphemy!:nuts:
     
  17. Richard King

    Richard King Active Member Active Member

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    I think he was kidding....lol...But on some real bad scored ways on BIG machines that I could not move to a bigger machine to have it machined I have ground them that way. One did a hardened CNC lathe bed on a machine in Arkansas that was burried inside a shop. It would have cost thousands of dollars to have hired riggers to move the machines in the shop to get it out of there. I used a small angled air grinder with detachable pads and ground it instead of scraping it. Same way with a straight-edge and bluing. A very fast " Power Scraper" LOL When I got it close I used diamond lapping compound and a lappng plate and stones. Then put Rulon on the matching way. It worked ok. And a i say "no news is good news" or hearing back from the customer. ha ha. They did have me back several times to teach some more classes after that. I am sure many of us have done somethings that some would shake there head at. But what is the saying about the mother of invention? Having a mind blank this morning. I will be off line a bit over the next couple of days as i will be traveling to Taiwan for my 30 years of teaching classes reunion. It should be fun and I will take some pctures. Everyone have a fun day scraping :) Rich
     
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  18. jmhoying

    jmhoying United States Active User H-M Supporter-Premium

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    I got a call from the re-builders this morning and he quoted $1600.00 for the repair. (Richard was right on with his guesstimate). He said that the cost reflects the fact that mine is worn a lot more than most they see. He knew that this wasn't really an option for me, since I also have some issues with head. (I'd be getting way more money into this machine that it'd ever be worth. (If it was a Bridgeport brand, I'd "probably" go ahead with it) He did suggest (as did Richard in a previous post) that I use some shims and find the thickness that the gibs would need added to them to make them more effective. They work with Trucite all the time and would gladly coat the gib with whatever thickness I need. I will probably go that route and see what kind of improvement I can get.

    Jack
     
  19. astjp2

    astjp2 United States Active User Active Member

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    Sounds like you have a good excuse to buy an Anderson scraper and a small camelback straight edge. Get it running and do the scraping later. Tim
     
  20. mws

    mws Active User Active Member

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    Jack,

    Too bad you're in Ohio. I'm doing almost the exact same repairs to a Bridgeport now. Yours sounds just like mine, measurments and all, except mine had a pretty paint job. Due to the price of professional rebuilding and the fact that I can't find anyone local to do a little pre-scrape planing, I'll be doing it myself. I took Richard's scraping class in September in Vermont and learned quite a lot. More importantly, I learned it's not an impossible undertaking. Getting all the measurement techniques down is more difficult than the scraping. Since I plan on restoring at least two lathes I currently have I bought a used granite surface plate and Biax machine scraper. The hand scraper, and CI straight edge I bought new and the bluing/spotting inks etc are relatively cheap. Altogether I thing I have about $1500 into scraping equipment. Gauges I already had and gadgets to use them I can make.

    I will be posting my progress, good or bad, on you tube. I figured others could benefit from what I'm learning. I will make a post here when I get the first video edited. We (my 14 year old and I) just shot it last night. Getting the mill done is my New Year's Project.

    I must say that the difference in performance of my lathe compound after scraping it in is substantial. No rock, far less chatter on big cuts and no binding at the ends of travel. I can't wait to get the cross slide done. I still need to scrape in a small CI Prism (can't have enough references).

    Good luck to you. I'll look in on your progress. Hello to you Richard and Happy New Year all.

    Mark
     
  21. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Richard hasn't posted here since 2013.

    I have participated in one of his scraping classes down here in Texas at Steve Watkins place at Navasota. I'm going to try to attend one of the days in February to see his new acquisition to his shop.

    By all means, show us your progress on the machines as you work on them. And please post lots of pictures.

    And if you hit a snag and can't figure out something, let us know, there are several of us highly knowledgeable in machine tool repair and reconditioning here and be willing to help.

    Ken
     
  22. Kernbigo

    Kernbigo United States Active User Active Member

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    Another quick fix for the gibb is to use slow drying epoxy glue, and adding plastic or micarta to the gibb back side, after checking with a feller gage to find out how much you need. I used to rebuild machine and we did that quire often. I f you want you can scrape the working side of the gibb flat also.
     
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  23. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    This is how I was taught to do it. I've also used thin steel flat bar that I knew was flat, and on smaller gibs, I've also used feeler gage stock if the gaps were less than .030", too, along with shim stock. Most were secured with Epoxy glue. Ken
     

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