questions on Bridgeport chrome ways and how to repair them
Close
Login to Your Account
Results 1 to 12 of 12
  1. #1
    Join Date
    Sep 2002
    Location
    Lawrenceville GA USA
    Posts
    6,175
    Post Thanks / Like
    Likes (Given)
    697
    Likes (Received)
    1315

    Default questions on Bridgeport chrome ways and how to repair them

    Ok I am sure this is covered in a book or some other media but I have a couple of questions about the chrome ways on the Bridgeport knee.

    One of my customers has a older BP in their shop and it has been rode hard and put up wet. They asked me to look at it and see if I thought it could be repaired. I wish I had taken some photos but I didnt have a camera handy.

    The previous owners must have never oiled it or took any kind of care at all. It looks like the chrome surface is very thin and in some spots, near the front of the knee, it is damaged and barely visible. There are some deep scars that are probably from chips that were allowed to be drug under the ways. And the flaking that can be seen is barely visible.

    1: Does the chroming really help or do machines with chrome ways still have to be fixed just as often as older machines or other machines that do not have the chrome ways?

    2: Can they be scraped or do you have to remove the chrome if it is worn to the point where it needs to be repaired? I would assume if the chrome is still there you could grind the ways but is that always necessary? If you do repair a knee that had chrome ways has anyone ever had them re-chromed after?

    3: Was the flaking done before the chrome or can it be done after? The one I looked at appears to have been flaked before but I am not really sure of that.

    4: Does anyone know how they chromed them in the first place? That is to say how do you selectively chrome the surface without chroming the whole part? And is there any idea of when they started chroming them in the first place?

    That is a bunch of questions at one time and this can be moved to the Bridgeport forum if it would be better to answer them there. Oh and if there is such a book that covers some of these questions I would like to know it. I have seen several books on the machines but I have never seen one in person so I dont know how useful they are. Anyone want to make a recommendation?

    Charles

  2. #2
    Join Date
    Apr 2001
    Location
    tucson arizona usa
    Posts
    5,057
    Post Thanks / Like
    Likes (Given)
    2188
    Likes (Received)
    4766

    Default

    The guys that I have seen who rebuild these things just scrap right over the chrome, no need to redo it.

  3. #3
    Join Date
    Jul 2005
    Location
    Cottage Grove, MN 55016
    Posts
    7,572
    Post Thanks / Like
    Likes (Given)
    4085
    Likes (Received)
    4518

    Default

    I have never seen anyone do a good job trying to scrape the chrome off. Never. I have tried with a Biax and it isn't a good way. It digs in and you get chatter like crazy. The way I have had success is to have the chrome stripped of at a chrome plating shop. Or have it milled off by cutting under it. The best way is to have it stripped. I would recommend this company Industrial Hard Chrome Plating Services | Wisconsin Chrome Plating Company as this is where all the local rebuilders have it done. It can be re chromed after you scrape it, but you have to file the sharp edges with a steep radius or the chrome will build up on sharp corners. Cal themup and ask themthe questions. But the shop has to have had experience doing it because if they don't mask the places where there are tapped holes or machines surfaces the chrome will stick. Also if they put to much on it will bubble up...and get rough like sand paper. Rich

  4. Likes Dresden liked this post
  5. #4
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    10,021
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2600

    Default

    now a days a lot of hard chrome plating is much more expensive due to hexavalent chrome fume exposure limits. the EPA rules in the USA
    .
    my old company had wheels 18 feet diameter 5 feet wide and about 20 tons. They were plated overnight. That is the fumes were so bad that everybody went home for the day (no night shift) and when they came in in the morning they shut it off. In China i saw plating places where the walls were all garage doors and they could all be opened. Basically just a roof to keep the rain out of the plating tanks.
    ,
    hard chrome i believe was done for 2 reasons. it takes longer to wear away and it lowers the friction coefficient so items slide easier.

  6. #5
    Join Date
    Sep 2005
    Location
    South Carolina USA
    Posts
    4,478
    Post Thanks / Like
    Likes (Given)
    2154
    Likes (Received)
    1307

    Default

    Just wondering.... How thick is the chrome on a BP? It can't be very much, or it would get uneven in a hurry...

  7. #6
    Join Date
    Jul 2005
    Location
    Cottage Grove, MN 55016
    Posts
    7,572
    Post Thanks / Like
    Likes (Given)
    4085
    Likes (Received)
    4518

    Default

    I could not remember how thick they put it on, so i called Todd at Indianhead Plating and he said they flash chrome .0003" to .0005" on and he said they used a special fixture to get it down in the dovetails. He also said that many of the longtime rebuilders aren't sending them as much. I would guess that because many machines now have hardened ways, chrome plating ways is becoming obsolete. Todd did say he could still do them if you needed it done, but the do more shaft plating now. Rich

  8. #7
    Join Date
    Jan 2007
    Location
    Auburn Ma
    Posts
    754
    Post Thanks / Like
    Likes (Given)
    25
    Likes (Received)
    58

    Default

    The chrome can be taken off with muriadic acid. This acid is also used to clean cement. It is a long process..
    JOHN

  9. Likes Richard King liked this post
  10. #8
    Join Date
    Jan 2007
    Location
    Auburn Ma
    Posts
    754
    Post Thanks / Like
    Likes (Given)
    25
    Likes (Received)
    58

    Default

    As far as I know...chrome can not be scraped off.....I take it off with acid....then wash with water to neutralize the acid. I have never had one re chromed. I suggest to customers to let me put turcite on both sides of the saddle....and rescrape all the cast iron....

    John Fahnestock
    J&L Scraping Service

  11. Likes bebop, CBlair, Richard King liked this post
  12. #9
    Join Date
    Feb 2005
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    330
    Post Thanks / Like
    Likes (Given)
    382
    Likes (Received)
    123

    Default

    Quote Originally Posted by sidecar580 View Post
    As far as I know...chrome can not be scraped off.....I take it off with acid....then wash with water to neutralize the acid. I have never had one re chromed. I suggest to customers to let me put turcite on both sides of the saddle....and rescrape all the cast iron....

    John Fahnestock
    J&L Scraping Service
    Yup thats what I do also ... ive never rechromed one either.
    Cheers Don

  13. Likes Richard King liked this post
  14. #10
    Join Date
    Nov 2002
    Location
    Burlington, NJ
    Posts
    1,340
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    101

    Default

    Hard chromed Bridgeports will outlast a non chromed machine by a factor of at least 3 to one if both are taken care of. I always thought it a terrible waste of money to purchase a machine without that option.
    My very first CNC, a Series 1 BOSS 6 with the true CNC iron (18 x 12 travel) was flat worn out and I was broke. Ways were worn badly but not scored at all, ballscrews loose, thrustbearings loose, head in bad shape. Head was easy, after all I was working for Bridgeport. The ways I carefully examined and determined since the wear was in the middle of the ways I could lap the ends down to match. Yep, hand lapped them down with a silicone carbide stone. Yep, took over a month working on it almost every night. Reloaded the ballscrews with over sized balls, shimmed the thrust bearings and relocated the bearing brackets. Rescrapped the non chromed members in for contact and squareness. Rebuilt the entire lube system. Gutted the control, cleaned everything so it looked like new and got it running. Ran that machine for 2 years and I paid for a good used Bridgeport machining center cash to replace it.
    Final accuracy when I was done was .0002 squareness per foot, less than 0.0002 backlash and it would hold 0.0005 all day. Purchased it for 500.00 and sold it 2 years later for 2500.00, still making excellent parts.
    To give you an idea of how bad the chrome was worn, the center of the knee to saddle ways were mottled, half chrome and half iron. When I was done, the entire area matched the middle, including the dovetails. The top of the saddle looked the same. I was a lot younger back than, don't think I have it in me to do that today.

    Bill

  15. Likes thermite liked this post
  16. #11
    Join Date
    Oct 2008
    Location
    Salisbury NC
    Posts
    6
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    1

    Default

    I made dams out of Modeling Clay and stripped mine with Muriatic Acid. The warmer the parts and Acid the faster it works. Be sure and neutralize acid with ammonia after rinsing with plenty of water . If not the acid keeps working , all though very slowly !

    Dwayne

  17. #12
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    25,739
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8118

    Default

    Quote Originally Posted by dunnitagain View Post
    I made dams out of Modeling Clay and stripped mine with Muriatic Acid. The warmer the parts and Acid the faster it works. Be sure and neutralize acid with ammonia after rinsing with plenty of water . If not the acid keeps working , all though very slowly !

    Dwayne
    +1 and .. also keep the acid's fumes away from you, the machine's bearings, electricals, etc.... and anything else remotely nearby that you value...

    Bill


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
  •