Repairing a Bridgeport table
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 28
  1. #1
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default Repairing a Bridgeport table

    I will be picking up a J-head Bridgeport mill after the governor lets us out of our houses again. It is my first full size mill.

    The table has a few marks of shame on it, including a nice rectangular pocket about 2 by 4 inches and 1/8 inch deep, milled right in the middle.

    It is only cosmetic for now because the vise or a work piece would cover them.

    I was wondering if anyone has repaired these things. Have you welded it and ground it down? Used some kind of filler? Inserted a plate and leveled it?

    Should I just shop for a replacement table?

  2. #2
    Join Date
    Apr 2004
    Location
    Shandaken, NY, USA
    Posts
    4,450
    Post Thanks / Like
    Likes (Given)
    1303
    Likes (Received)
    7305

    Default

    Frank R

    I'd avoid welding or brazing to fill or patch the hole in the Bridgeport table. The table is cast iron, and has been machined over its length for dovetails as well as the top and side surfaces. Welding or brazing (due to the table being cast iron) will put heat into the table, and will also set up stresses when the patched area cools. The result of this post-weld (or post brazing) stress is going to be the equivalent of putting a turnbuckle on the top surface of the table, and can pull the table from flat into a "camber" or curve with the concave side on the table top. Any accuracy in the table will be lost.

    I'd also steer clear of patching with epoxy resins such as Devcon or Belzona offer. While these products have some good applications, patching a Bridgeport table is not one of them I'd recommend. Aside from all else, the makers of these repair resins will invariably insist that the "substrate be properly prepared by blasting to a white metal surface" to prevent their resin peeling off. These resins are generally some sort of epoxy resin with fine particles of various metals such as iron, steel, bronze- depending on application. They are quite pricey.

    I'd go with the tried-and-true method of "letting in a patch". Since there is already a cavity milled into the table surface, if you are determined to repair it, a "flush patch" will work. It may mean milling the cavity a bit deeper ( say 1/4"- 5/16") and squaring the sides and ends. Once this has been done, a patch is made from steel plate a little thicker than the depth of the cavity. This patch is carefully fitted to a snug fit in the cavity (may have to be driven in using light blows from a brass hammer or similar). Making the patch a little oversized and filing to final dimensions is not a bad idea. Putting a chamfer on all the bottom corners is also a good idea so the patch sits down solidly in the cavity.

    When the patch is is fitted, it can be drilled thru for some socket head screws, with holes spotted into the bottom of the cavity and tapped. On larger work, special screws or "patch bolts" are often used. These have heads to fit in a countersunk hole with an extended shank above the head having an undercut. The patch bolts are driven in using a wrench on this extended shank and depending on design of the patch bolts, either the shank is twisted off or else cut off. The head of the patch bolt is then dressed flush with the adjoining surfaces. For your purposes, some flathead socket screws will be fine if you do not mind seeing the hex socket holes in the finished repair.

    Once you have the patch secured in the cavity with the screws, it can be carefully milled off flush. To do this, you will need to "tram the head" of your Bridgeport (indicating the head so it is dead square to the table in both directions). I'd use a "fly cutter" with a toolbit having a small radius on it to get a fine surface finish on the patch. Using a surface gauge and dial indicator, you then check the surface of the patch for difference in height with the surrounding table. My own way would not be to attempt to mill the patch right to the same plane as the table. Rather, get it within a half thousandth higher or thereabouts and finish by scraping and stoning. Using a dial indicator held on the head of the Bridgeport, cranking the table in the X & Y direction with the indicator contacting the table and patch will tell the tale of any localized areas on the patch which are higher than the table. Careful scraping or stoning will bring these "plateaus" down. The end result will not be as pretty as an undamaged table surface, but it will be as good. We are not trying to get a perfect surface on the repair with 100 % flatness and 100% of it all at the correct height to be in the same plane with the surrounding original table surface. Rather, a series of small "plateaus" so that 80-90% contact is fine.

    The repair will be obvious, but it will be 100% functional and will allow you full use of the table surface. If you find a used table from another Bridgeport, chances are it would work "as is". I tend to think the real possibility is that you might find wear on the replacement table's dovetail surfaces requiring "scraping in" of both the dovetail on the used table and in the saddle of your Bridgeport. Used machine tool parts like tables and saddles tend to wear into each other.

    For the near term, I'd suggest two pieces of old mechanic's or engineer's wisdom:

    "If it runs good, don't mess with it"
    and,
    the "KISS" principal: "Keep it simple, stupid !"

    In short, if you can use the Bridgeport as it is with the cavity in the table surface, live with it. The effect is cosmetic for the most part. If you have a running Bridgeport when you get it home, put it to work and don't worry about the table surface. In time, as you get familiar with your Bridgeport and perhaps build skills needed and have some free time on your hands, you can then get around to the patching job.

    The KISS principal applies to the patching, as you use the Bridgeport to fix itself and you use very basic and simple methods.

  3. #3
    Join Date
    Sep 2005
    Country
    UNITED STATES
    State/Province
    West Virginia
    Posts
    4,028
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    442

    Default

    I had good success repairing some holes in a Benchmaster milling vise using JB Weld. Nothing as big as what you have to fill, and the vise is easier to get properly clean. But it might be worth a shot.

    Andy

  4. #4
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default

    Thanks Joe. I feel honored that you responded to one of my questions with one of your legendary answers.

    I won't be getting to any repairs any time soon. It will probably be in storage for at least a year while we buy our next house.

    I am also a believer in the KISS method.

    I like your idea of bolting in a plate. I have some machine shops around here. I might be able to get the table ground flat for a nominal fee.

    Another idea occurred to me: I have some experience as a boat builder using epoxy. I thought I could use a die grinder to rough up the bottom, epoxy in a carefully fitted patch, and then put a magnetic base from a surface grinder on top. This would pull the patch up to table level while the epoxy cures. Putting a layer of vinyl between the top and the magnet will prevent any epoxy from sticking.

    I could probably do a similar thing with set screws. Kind of like leveling a router base plate on a router table.

  5. Likes Joe Michaels liked this post
  6. #5
    Join Date
    Apr 2011
    Location
    Nebraska
    Posts
    1,288
    Post Thanks / Like
    Likes (Given)
    1907
    Likes (Received)
    397

    Default

    I would think you should avoid epoxy all together as it is heat sensitive and can also be affected by humidity or oils. Bolting in a plate and cutting/grinding flush to the table really seems like the best and easiest solution.

    JMHO

    -Ron

  7. Likes Joe Michaels, HWElecRepair liked this post
  8. #6
    Join Date
    Nov 2008
    Location
    Madera county california usa
    Posts
    2,531
    Post Thanks / Like
    Likes (Given)
    21
    Likes (Received)
    639

    Default

    There are some epoxies rated for hvac coil repairs, not cheap but good stuff.

    You can collect some powdered steel from your bench grinder and clean it with acetone.

    A magnet can be used to get just the steel.

    Clean holes with acetone and mix batch of epoxy.

    Use it slow setting as it is stronger and it allows time to mix in the iron you just cleaned.

    Make a batch large enough to over fill a bit and insure mixed very well.

    The iron gives extra strength to the fill.

    Get it worked into the void and insure it is taller than the table.

    Let it cure a week or so then file it down.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  9. #7
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default

    Quote Originally Posted by MetalCarnage View Post
    I would think you should avoid epoxy all together as it is heat sensitive and can also be affected by humidity or oils. Bolting in a plate and cutting/grinding flush to the table really seems like the best and easiest solution.

    JMHO

    -Ron
    Some epoxies are heat sensitive, I have softened them to remove excess using a heat gun. However, they known to be quite resistant to humidity and many chemicals.

  10. #8
    Join Date
    Jul 2001
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    2,003
    Post Thanks / Like
    Likes (Given)
    187
    Likes (Received)
    415

    Default

    In some recent shop adventures I have done some soft soldering
    of cast iron to repair some damage.
    There was a scratch (scoring) in the V way of one of my lathes.
    The V way was otherwise in fine shape, with little wear.
    So to keep chips and such out of the score, I used 2 propane
    torches and heated the bed locally. It took some time to get
    things up to temperature to flow. But it took 10 minutes maybe.
    I used 50/50 Tin/Lead solder and zinc chloride flux.
    Results were good, but I did need to abrade the score with a
    scratch awl to get the solder to adhere well.

    Another time I was soldering a brass shim to a small cast iron
    plate. I was going to tin the brass shim and the iron plate
    and then sweat them together. The brass took the 50/50 solder
    with no problems. The iron plate had places where the solder
    would stick and other places where it would not. Yes very clean
    and used flux, da da da.
    So I tried a different solder and it worked wonderfully.
    What I used on the iron plate was the new lead free pipe solder.
    It was 95% tin and 0.4% silver, and ~4% copper, I guess as a filler.
    I believe the reason it wetted out so well might be the silver.
    Mind you, this us still soft solder and I used a propane torch
    for heat. So if doing machine table repair, or any other cast iron
    repair, try silver plumbing, lead free solder. Plumbers used to scoff
    at it in the beginning, perhaps holding on to tried and true old school
    50/50 solder as what worked. But I really like the lead free solder for
    how it seems to stick to cast iron. Maybe my experience will help you.

    --Doozer

  11. #9
    Join Date
    Nov 2007
    Location
    marysville ohio
    Posts
    9,805
    Post Thanks / Like
    Likes (Given)
    2810
    Likes (Received)
    6492

    Default

    Quote Originally Posted by Frank R View Post
    I will be picking up a J-head Bridgeport mill after the governor lets us out of our houses again. It is my first full size mill.

    The table has a few marks of shame on it, including a nice rectangular pocket about 2 by 4 inches and 1/8 inch deep, milled right in the middle.

    It is only cosmetic for now because the vise or a work piece would cover them.

    I was wondering if anyone has repaired these things. Have you welded it and ground it down? Used some kind of filler? Inserted a plate and leveled it?

    Should I just shop for a replacement table?
    Treat it like a sore dick.....don't f*ck with it!

  12. Likes Joe Michaels, kustomizer liked this post
  13. #10
    Join Date
    Sep 2006
    Location
    Sacramento County, California
    Posts
    3,925
    Post Thanks / Like
    Likes (Given)
    2455
    Likes (Received)
    1391

    Default

    When I got my Webb Mill and was refurbishing it, there were some small nicks on the table. I filled them with JB Weld and then flattened the excess with a file after the JB set up. After some years, you can hardly tell where they are.

    The OP has a special problem, however, with that large of a divot. Joe Michaels' method seems to me to be the best idea.

  14. Likes Joe Michaels, MetalCarnage liked this post
  15. #11
    Join Date
    Oct 2006
    Location
    Norfolk, UK
    Posts
    875
    Post Thanks / Like
    Likes (Given)
    867
    Likes (Received)
    355

    Default

    I did this same thing many years ago with a little "Abwood" machine vice that had been used as a drill vice-I milled out the drilled part,let in a piece of 1x1/4 and scraped level. Still good 40 yrs later

  16. Likes Joe Michaels liked this post
  17. #12
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default

    I managed to get some photos sent to me. It is not how I remembered it but you can see for yourself.

    IMG_4654 by frank7748124, on Flickr

    IMG_4652 by frank7748124, on Flickr

  18. #13
    Join Date
    May 2011
    Location
    southern in.
    Posts
    1,506
    Post Thanks / Like
    Likes (Given)
    2005
    Likes (Received)
    406

    Default

    Leave it alone, it's just another slot. Not pretty, but will never hurt you.

    JH

  19. Likes kustomizer liked this post
  20. #14
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default

    Joe and others, in light of the photographs, would you still recommend a patch?

  21. #15
    Join Date
    Aug 2012
    Location
    Lower Thumb, Michigan
    Posts
    237
    Post Thanks / Like
    Likes (Given)
    53
    Likes (Received)
    170

    Default

    I'm going to agree with the guys saying to ignore it.
    Ugly, yeah, but the only one who should lose sleep over it is the one who did it.
    Devalues the machine as to selling/buying price, but 90% of Bridgeport work is in a vise, and a vise will hide most of the shame.

    If that rare case comes up that the flaw would interfere with set-up, then, I'd consider patching it.

    Mike

  22. #16
    Join Date
    Jul 2001
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    2,003
    Post Thanks / Like
    Likes (Given)
    187
    Likes (Received)
    415

    Default

    Quote Originally Posted by rustyironism View Post
    ….. but 90% of Bridgeport work is in a vise,.....
    Mike
    What are you? A home shop machinist? You just tipped your hand.

    --Doozer

  23. #17
    Join Date
    Sep 2006
    Location
    Sacramento County, California
    Posts
    3,925
    Post Thanks / Like
    Likes (Given)
    2455
    Likes (Received)
    1391

    Default

    Quote Originally Posted by Doozer View Post
    What are you? A home shop machinist? You just tipped your hand.

    --Doozer
    Ha, you sound just like a guy with the same name as you over on the HSM site. I used to be on there under a different name and you sound just like him (or her).


  24. #18
    Join Date
    Mar 2005
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    4,666
    Post Thanks / Like
    Likes (Given)
    1208
    Likes (Received)
    1098

    Default

    Although 90% is high, even in a real job shop it's still probably at least 70% of work in a vise easy. The rest in my experience is either in an indexer or super spacer (including rotary tables here also) or mounted on the table on parallels and separate clamps. All could easily avoid that one middle area by simply swinging the head if necessary.

  25. #19
    Join Date
    Apr 2004
    Location
    Shandaken, NY, USA
    Posts
    4,450
    Post Thanks / Like
    Likes (Given)
    1303
    Likes (Received)
    7305

    Default

    My 2 cents on this question: Leave it alone. The milling into the table is relatively shallow and not of a large enough area to affect about 99% of the jobs you are likely to do on that Bridgeport. The machine is hardly "cherry" nor is it a toolroom machine. Vises, rotary tables, indexers and similar will span the damaged areas, or simply can be located on either side of them. Larger jobs to be clamped directly to the table are usually setup on 1-2-3 blocks, matched heavy parallels, or on a variety of other things such as hardwood (for rough castings), shims (for oddly shaped worked), planer jacks (aka jack screws) and anything else that works to support a job so it can be clamped to the table. On some really oddly shaped work, a few points are supported on shop-made fixturing, and it becomes a matter of indicating a reference surface and/or "picking up a center location" on the work. In those kinds of jobs, the condition of the table becomes irrelevant.

    I remachined a Norton motorcycle crankcase half a couple of winters back. It had no real good surfaces to lay on the table of the mill to clamp down. It was a case of setting up on simple shop-made fixturing (keep plenty of scrap steel and aluminum at hand for jobs like these, and being handy with welding does not hurt). A main bearing counterbore and crankshaft seal counterbore had been damaged. These were bored oversized, and a new "pad" for the seal counterbore was TIG welded to the crankcase. The maain bearing counterbore was built up with TIG welding. I had to re-establish centerline of the crankshaft in the crankcase half, and get it squared with the split joint of the crankcase. There was no clamping anything directly to the table, but supporting it on some fixturing I'd made, then using shim stock between the base of the fixturing and the table to bring the split joint surface into square with the spindle of the mill.

    Another exercise which can lead to temporary insanity, which I call "chasing my tail", is tramming the head of the mill so it is dead square to the table in two directions. I use two "match lapped" parallels which are 1" x 2" x 12" laid across the table to indicate off of when I tram the head. I use a home-made "tramming bar" to hold a dial indicator. The parallels span the width of the table, so even if there were localized damage, those parallels catch the plateaus or high spots.

    I tram the head of my Bridgeport anytime I shift the ram position, and before finer jobs such as boring or work calling for close tolerances. I "kiss off" the table with an Arkansas Hard oil stone (a white stone that is so smooth you'd swear it would not remove any metal). This gets rid of any small burrs. Tramming the head of a mill is good exercise in use of dial indicators. Invariably, you find that last thousandth does not quite want to be adjusted out. You give the adjustment to the angle of the head "one little tweak" and discover the indicator is now reading somewhere out in left field. After a few times, tramming the head gets to be more routine. It's good practice to check the head of a Bridgeport if you have adjusted position of the turret (base of the ram) or the ram itself, or if you are returning the head to square after having done a job with it at an angle.

    You will be quite surprised at how little, if any, difference the damage to the table makes when you get into using your Bridgeport. I'd suggest taking an India Medium Hard small oil stone and lightly stoning off the table. Using a circular motion and keeping the table wet with something like penetrating oil or kerosene, the stone is worked over the whole table, trying to be as uniform as possible. The object is not to remove any significant metal from the table, but to take down any burrs or "dings" (raised metal created when something harder was dropped against the table or driven into it). Use the heel of your hand to lightly run over the table to feel for any burrs. Once you have stone off the table, Tramming-in the head is a good idea. This will get you setup for most milling and drilling operations. Before you mount a vise on the table, stone off the bottom of it as well. If you store a vise or other tooling off the mill, it is a good idea to put a soft wood board (pine) between the bottom of the vise and the floor or shelf it is going to be stored upon. A steel shelf or concrete shop floor is likely to raise burrs or put some dings into the bottom of a cast iron vise or rotary table or similar.

    I keep several oil stones handy in my "roll away" machinist chest. These have various shapes, and most are "India Medium Hard", with a few small "Arkansas Hard" stones as well. Good work habits will go a whole lot further in producing good work than a pretty table with no visible damage, IMHO.

    Plainly, while a table free from visible damage is pleasing to the eye and may make a person feel good, it is not a necessity for doing fine work.

  26. Likes Jim Christie, Frank R liked this post
  27. #20
    Join Date
    Dec 2009
    Location
    Dearborn, Michigan
    Posts
    1,335
    Post Thanks / Like
    Likes (Given)
    100
    Likes (Received)
    242

    Default

    Thanks again Joe.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •