Bridgeport saddle rescrape questions

Maschine · Mar 22, 2017

I recently bought a late 60's Bridgeport mill with a 42" table. It has chromed knee ways and chromed table ways. The saddle does not appear to have any chroming on either side. The knee and table ways appear to be in decent shape with chrome and flaking intact. The saddle X and Y ways have flaking in the center third, but the flaking is mostly worn away on the outer thirds. So I'm considering having the saddle X and Y ways re-scraped to freshen them up.

I don't know of any reputable machine rebuilders in my area (Maryland). I know of some a couple hundred miles from me (like John Fahnestock). Is it possible and/or advisable to have the saddle rescraped without also having the knee and table to match it to? Like I said, the table and knee ways are in good shape and since they're both chromed I wouldn't have them reworked.

Reason I ask is that I can ship the saddle alone for rework much easier and at a much cheaper price than having to ship the saddle along with the knee, table and maybe even the column/base.

Richard King · Mar 22, 2017

From my experience in rebuilding chromed Bridgeport ways. The table and column are not chromed. The back, top, dovetails and gibs of the knee are. The top, bottom and dovetails top, bottom and Gibs on saddle are. The best way to do it is to have the chrome stripped off in an acid bath at a Chrome Platter company. The top of the saddle is worn on the ends as the table is bent high in the middle of the top because of over tightening of the T-nuts inside the T-slots as Professor Archie C. has taught us. pus the ends wear as there are no way wipers on that axis.

Most of the time the top of the knee and it's dovetails are worn in the middle and a simple way to check it is to tighten the gib up when the saddle is in the middle of the knee and then try to move it out or closer to the operator and then toward the column and see if it gets tight. In all of the ones I have tested the knee is worn in the middle. It is possible I guess that the machine was only run in the X in some sort of production run and the top of knee didn't wear.

In order to do it right in my opinion. Is to have the chrome stripped off Knee, saddle and gibs and as you do that the paint will strip off everywhere too. Have the table planed & Scraped or ground and the saddle ground or milled so it is perfectly parallel and dovetails square top to bottom of it. Then match fit ways and gibs.

Another method is to mill & grind off the chrome, but it is rough on cutters. You need to cut under it.

I also have found re-chroming scraped ways is not worth the effort as most chrome platter's don't do it right and you get build up of the chrome on sharp edges or they put to much on and it gets a bubble effect.

So with all this in mind you may want to just clean it up replace the BiJur units and use it as is.
I have no clue on rebuilders, but I would bet members Paolo or Dee who both live near Baltimore will know someone. If not you should call around to local machine shops and ask them. I wish I could be more help. Rich

PS: Out Here in the North Central US, there is a really good rebuilder named A&D Machine Rebuilding who does several Bridgeports a year.

Maschine · Mar 23, 2017

Thanks Richard, I really appreciate your thoughts and advice. Unfortunately I don't seem to have a reputable machine rebuilder in my area (Maryland), so if I did want to have my mill reworked, I would have to ship it via freight to elsewhere in the country and back. That can double the price and therefore quickly become prohibitive. So perhaps just reassembling my machine and using it as-is is my best option. I'm a total amateur hack machinist anyway, so I doubt I would know the difference. I was just hoping this machine was in better shape to start out with. I only wanted to buy one mill in my lifetime and was hoping this was it.

You can see images of the chromed table ways below:

The chrome knee ways are still mostly intact, but they do show some wear...

The saddle also shows wear and does not appear to be chrome, which I guess is a departure from what most Bridgeports are??

Maschine · Mar 23, 2017

Few more saddle pics...

So I'm wondering if it would be possible to send the saddle out alone and have it scraped flat and square without having it matched to the knee or table. Probably not, but just a thought.

Tyrone Shoelaces · Mar 23, 2017

Richard King said:
From my experience in rebuilding chromed Bridgeport ways. The table and column are not chromed. The back, top, dovetails and gibs of the knee are. The top, bottom and dovetails top, bottom and Gibs on saddle are. The best way to do it is to have the chrome stripped off in an acid bath at a Chrome Platter company. The top of the saddle is worn on the ends as the table is bent high in the middle of the top because of over tightening of the T-nuts inside the T-slots as Professor Archie C. has taught us. pus the ends wear as there are no way wipers on that axis.

Most of the time the top of the knee and it's dovetails are worn in the middle and a simple way to check it is to tighten the gib up when the saddle is in the middle of the knee and then try to move it out or closer to the operator and then toward the column and see if it gets tight. In all of the ones I have tested the knee is worn in the middle. It is possible I guess that the machine was only run in the X in some sort of production run and the top of knee didn't wear.

In order to do it right in my opinion. Is to have the chrome stripped off Knee, saddle and gibs and as you do that the paint will strip off everywhere too. Have the table planed & Scraped or ground and the saddle ground or milled so it is perfectly parallel and dovetails square top to bottom of it. Then match fit ways and gibs.

Another method is to mill & grind off the chrome, but it is rough on cutters. You need to cut under it.

I also have found re-chroming scraped ways is not worth the effort as most chrome platter's don't do it right and you get build up of the chrome on sharp edges or they put to much on and it gets a bubble effect.

So with all this in mind you may want to just clean it up replace the BiJur units and use it as is.
I have no clue on rebuilders, but I would bet members Paolo or Dee who both live near Baltimore will know someone. If not you should call around to local machine shops and ask them. I wish I could be more help. Rich

PS: Out Here in the North Central US, there is a really good rebuilder named A&D Machine Rebuilding who does several Bridgeports a year.

That's good advice. I'd just add that another reason you get wear on the outer ends of the saddle in the long travel direction is that when the table moves to the extreme ends the loading on the saddle ways increases dramatically.

From my experience there are chrome platers and then there are machine tool chrome platers. There are quite a few of the former and hardly any of the latter.

Rich is correct in saying that if inexpertly applied you will get a really noticeable build up of chrome on the edges of what ever you are plating. He's also correct in saying the de-chroming process is very hard on whatever you're working on. Strong acid is used in the process and it will probably make a real mess of the paintwork.

Are your machine's ways causing you problems or are you just hankering to return it to as new condition ?

Regards Tyrone.

dcsipo · Mar 23, 2017

Richard King said:
From my experience in rebuilding chromed Bridgeport ways. The table and column are not chromed. The back, top, dovetails and gibs of the knee are. The top, bottom and dovetails top, bottom and Gibs on saddle are. The best way to do it is to have the chrome stripped off in an acid bath at a Chrome Platter company. The top of the saddle is worn on the ends as the table is bent high in the middle of the top because of over tightening of the T-nuts inside the T-slots as Professor Archie C. has taught us. pus the ends wear as there are no way wipers on that axis.

Most of the time the top of the knee and it's dovetails are worn in the middle and a simple way to check it is to tighten the gib up when the saddle is in the middle of the knee and then try to move it out or closer to the operator and then toward the column and see if it gets tight. In all of the ones I have tested the knee is worn in the middle. It is possible I guess that the machine was only run in the X in some sort of production run and the top of knee didn't wear.

In order to do it right in my opinion. Is to have the chrome stripped off Knee, saddle and gibs and as you do that the paint will strip off everywhere too. Have the table planed & Scraped or ground and the saddle ground or milled so it is perfectly parallel and dovetails square top to bottom of it. Then match fit ways and gibs.

Another method is to mill & grind off the chrome, but it is rough on cutters. You need to cut under it.

I also have found re-chroming scraped ways is not worth the effort as most chrome platter's don't do it right and you get build up of the chrome on sharp edges or they put to much on and it gets a bubble effect.

So with all this in mind you may want to just clean it up replace the BiJur units and use it as is.
I have no clue on rebuilders, but I would bet members Paolo or Dee who both live near Baltimore will know someone. If not you should call around to local machine shops and ask them. I wish I could be more help. Rich

PS: Out Here in the North Central US, there is a really good rebuilder named A&D Machine Rebuilding who does several Bridgeports a year.

Sorry, i know no rebuilders in the area. But do not despair, if you have flaking left on your knee and table ways it probably means you have no more than a thou or two wear on them. That gets you to the saddle. That you can map out and on a small surface plate and get some decisions about what you want to do. We measured the saddle of a BP at Tuckahoe that seemed more worn but in reality was out only about 0.001" I would put together the mill and make a few parts and decide what needs to be fixed based on what it produces. Personally i would not touch the machine till i know what it does in real world situations.

dee
;-D

Richard King · Mar 23, 2017

I can't recall ever seeing a Bridgeport 1/2 moon flaked on the knee clearance surface that came from the factory. So some rebuilder or used machinery dealer did a partial rebuild. If your not holding tight tolerances I would use it or if you need to hold tighter tolerances, I would sell yours and buy a Acer, Kent or good quality Taiwanese mill. A friend of mine who rebuilds Bridgeport's told me he can rebuild one nowadays cheaper then a new Acer.

Maschine · Mar 24, 2017

Thanks all. Sounds like I should just clean everything up, put it together and see what I have. The machine seemed tight when I physically inspected it prior to purchase. I wasn't aware that the scraped surface on the upper knee clearance area is not factory. I am now and have learned a lesson. As you all have suggested, depending on how well the machine works, maybe I'll have it reworked at a later date or just live with it if it still makes good parts. Thanks again.

Colin Heath · Mar 25, 2017

I,m far from an expert, in fact complete amateur as far as machine tool rebuilds but as Richard says, that flaking in middle of the saddle ways does not usually appear and is not indicative of the wear on the saddle.

From the work I have seen, the middle of the way is relieved to prevent table rock so the flaking would remain here as it should never contact (which makes you wonder why it was flaked).

The rest of the machine looks a lot less worn than mine and that's not the end of world.

Richard King · Mar 25, 2017

Colin Heath said:
I,m far from an expert, in fact complete amateur as far as machine tool rebuilds but as Richard says, that flaking in middle of the saddle ways does not usually appear and is not indicative of the wear on the saddle.

From the work I have seen, the middle of the way is relieved to prevent table rock so the flaking would remain here as it should never contact (which makes you wonder why it was flaked).

The rest of the machine looks a lot less worn than mine and that's not the end of world.

They just flake it as it is easy when your doing it to keep pushing, moving along and looks good. Remember to only relieve the middle out of the shorter side. Have to check the distance of travel too, as some short screw machine slides move past the 30% .

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