Bridgeport bearing help

[Jangaard]

I am looking for suggestions for getting a bearing replaced on my Bridgeport. I am not sure what model I have but is does have a veri drive on it. I don't really want to learn how to replace the bearing and/or bearings myself. If anyone has a phone number for someone in my area (Torrance Ca.) who is fair, and can replace the bearings would you please E-mail me with his contact information. Jangaard@socal.rr.com .

Thank you very much.

[snakebit95]

Do you know which bearing is bad? Perhaps you can remove the component and have a machine shop replace the bad bearing. It would be much cheaper than having a service person do it at your home/shop. Just throwing-out another option that you may or may-not have thought of. The Bridgeport heads are pretty easy to disassemble (if not the spindle bearings), and you could easily take the piece to an automotive machine shop to have the old bearing removed / replaced. Hope this helps!!

Wayne

[Jangaard]

Thanks Wayne, did not think about that. Still looking for someone to replace it though. I might have to learn to do it myself.

[NC Cams]

I can tell you an exact or at least a reasonably equivalent bearing to use BUT, I need the OEM part number for the bearing. My info is based upon OEM bearing drawings that I acquired over the years.

You've not provided enough information to figure out which specific bearing you need/want.

BTW, the type of finesse and/or technology that's required to redo machine tool isn't necessarily endemic to that found in some "pound and grind" machine shops.

You really need to find a machine tool spindle repair shop if it is the spindle that you're fixing. You shouldn't just replace the bearings. It is common and PROPER practice to regrind the spindle taper true after replacing the bearings - that's how they built them, that's how the factory rebuilt them, folks who don't do it that way won't necessarily get what they're hoping for via a mere bearing change.

In closing, with proper care, you should be able to pretty near install any shaft mounted bearings with judiciously applied heat and/ice. Hammars and/or presses should be avoided for assembly.

[Jangaard]

Originally Posted by NC Cams I can tell you an exact or at least a reasonably equivalent bearing to use BUT, I need the OEM part number for the bearing. My info is based upon OEM bearing drawings that I acquired over the years. You've not provided enough information to figure out which specific bearing you need/want. BTW, the type of finesse and/or technology that's required to redo machine tool isn't necessarily endemic to that found in some "pound and grind" machine shops. You really need to find a machine tool spindle repair shop if it is the spindle that you're fixing. You shouldn't just replace the bearings. It is common and PROPER practice to regrind the spindle taper true after replacing the bearings - that's how they built them, that's how the factory rebuilt them, folks who don't do it that way won't necessarily get what they're hoping for via a mere bearing change. In closing, with proper care, you should be able to pretty near install any shaft mounted bearings with judiciously applied heat and/ice. Hammars and/or presses should be avoided for assembly.

Finding the bearing once it is out will not be the problem,,, I just didn't want to get half way into trying to rebuild it myself (for the first time) and run into a problem, or worse yet miss something simple because I am not experienced. I wanted to find someong local that could do the job, but from the looks of it (no leads yet from readers) it looks like I am going to have to tackle it myself.

[snakebit95]

If you have a digital camera, you can take some photos of it as you disassemble it. Put all the pieces in sandwich bags and label each bag with a Sharpie marker. This is how I work on big projects for my first time. It has always worked well. I agree with NCCams, if it is a spindle bearing it will require a machine tool rebuilding shop to properly do the repairs. In this event, you can usually ship the entire spindle assembly to a shop for rebuild. Any other bearings can probably be removed / replaced by an automotive machine shop without too much trouble / worries.

[NC Cams]

Do NOT THINK FOR A MILLISECOND that the "numbers" printed on the bearing tell you what it is - ESPECIALLY if it is a spindle bearing.

The OEM bearings (both spindle an OTHER positions) were MADE FROM generic bearings BUT they underwent special certification inspection and/or precision matching to get them to work properly.

It's your machine - do what you want. If it is the spindle however, you could end up creating a miserable first rebuild experience that could get expensive.

[snakebit95]

NC,
Man......you are a bit tough on the new guys......ahh?? I can understand your point if this guy had a $50K machining center, but it sounds as if this is a Bridgeport knee-mill. I think they are pretty easy to work-on, and I have tackled a few spindles in my days on these machines. They are not that difficult to work on (in my opinion). Yes, the spindle is an area that I would recommend a shop with experience to repair. I always try to encourage people to look under the covers and see how things work; especially if it is a hobby machine in his garage / workshop. If he was making a living from this machine, he would not be on a hobby site looking for help. I really respect your feedback though, since you have helped me in the past a few times. However, I think you may have scared the guy with that last post - LOL.

[NC Cams]

I'm that way for a good reason and for reasons of purely good intent.

I used to be a bearing service engineer and dealt with guys who bought generic bearings. About every other week or so, one would call to crab about "my junk" bearings not working right in their mill.

When asked how they got the p/n's, the answer was INEVITABLY "from the number etched on the bearing, of course you idiot".

Hmmm, they bought generic bearings based on a generic part number and now were harping to me because it didnt work right. Like asking for a tire - what kind? don't matter, don't care, they all work the same as long as they hold air. Really???

Little did they know that Bridgeport, ESPECIALLY IN THE GENERATION OF MILLS HE"S DEALING WITH, used size coded OD's and ID"s in most any precsion rotating position.

They then went to the trouble of high point marking them and other tricks to come up with psuedo machine tool grade bearings from hardware store bearings. If you didn't use the comparable bearing (w or w/o spindle ID regrind) the spindle perfformance sucked. YOu alslo had to go thru 10-12 sets to select the bearings that would match up properly. Precision by musical chairs. No wonder they went bust.

If you did the same thing on the ball screw/lead screw support bearings (they used generic cores and precision preloaded them via selective fit), you got sloppy backlash that you could not get rid of.

Hmmm. The bearings my employer may have sucked after you got thru with them but that's because YOU bought the wrong ones using WRONG assumptions. The didn't suck until you mis used them

Unlike a lot of 'experts', I have copies of the OEM bearing design specs for most of the BPT bearings. I've listened to well intended guys give me their resume's over and over outlining their expertise about machine tools and the rebuilding thereof - the same guys with poor peforming machine rebuilds..

Yet, they put in new bearings and it rattles, has sloppy housing and or spindle fits and chatters like a baseball card in a bicycle spoke when it cuts. All becaue my employers bearings are/were junk.... I don't think so, actually I KNOW SO.

Having been at Hardinge and at numerous spindle shops and seen what the GOOD outfits do to redo a BPT mill to re-establish new factory specs, I now know why some guys always had issues.

When I've talked with old time BPT field service who knew the guys in the now defunct BPT OEM spindle shop, they admitted knowing of the special stuff that went on but since it was supposedly "secret", they never really dug too deep to find out. After all, the guys did respect each other's talents and did protect their buddy's source of income by doing so.

Sorry if the member was offended. He's welcome to have a go at installing bearings. My information and precautionarey rant remains posted. Why? Because I"ve been down the path of well intended but incorrect component useage path TOO many times before and I'm only trying to prevent it from happening just 1 more time.

As is always the case, the reader is permitted to follow or ignore any suggestions made by a contributor to the CNC Zone. This is but another of those cases.

[snakebit95]

NC,
Once again......a lot of good information in your post. I had no idea that Bridgeport matched the bearings as you state. From a design stand-point, if a system requires a certain precision of alignment or flatness, it would be so stated on the assembly / manufacturing drawing. In this case, I would think a higher class bearing or level of machining would be required. Then again, if you neglect the design standpoint (the Design Engineer's view) and consider the cost standpoint (the bean-counter's view), I can see where measuring and grouping bearings by critical features could occur to save a few pennies. Personally, I am happy to see such experienced individuals as yourself surfing this forum. Your feedback is a big part of making this forum fun to read; even if you do tend to scare the new members <chuckling>

[NC Cams]

How to make a quality part:

1. Design and build quality via good component sourcing and do it right the first time assembly.
or
2. Design quality, buy cheap, inspect until blue in face, sort parts, redo until it works, it'll never work right again if all the secret magic used to make it work isn't put back in during service thereafter.

When you expect 1 but get 2, and can't understand why something doesn't work when you did it "right" cause you "do know what you're doing", it must be bad parts, right? Sadly, it ain't always that way....

We all pick up traits from people we admire as we go thru life. The "scared straight" aspect of my persona came from one of my very first engineering managers. He was a crass old SOB who challenged everything you did. Each design review was an inquisition, not a reviw. After about the 4th or 5th "did you consider this?" in the review, you learned his pattern and what he was protecting via his poor bedside manners - it was his way, cuz that's how he was taught, of maintaining impecable product quality by demanding higher and higher attention to details on the part of his product engineers.

Result: the parts were considered the finest out there and, although not necessarily the lightest or trickest (the company did do a lof of "racing parts"), they worked well and could be relied upon to be functional and just as good in Seattle as they were in Daytona Beach - the "mcdonald's hamburger" method of maintaining consistant product quality.

I was taught to fear electricity until I gained respect for it. I still fear it but I do respect it more now than ever. If a member gets to a point where a little voice from somewhere goes, "what would NC say about this???" when they go to do something, I've succeeded.

At that point, life don't get any better as I've passed something about about method #1 on....

To the member who started the thread: Did you figure out the OEM bearing number yet???? There should be a model number and an exploded drawing and parts list out there someplace to help you figure out exactly what you need. I'm pretty sure Production Tool's huge catalog lists BPT's OEM part numbers.

[karlden]

One of the issues with bearing replacement is, as already noted, the resulting TIR of the taper. The following business that specializes in re-grinding spindle taper seats in-place on the machine explains this in their advertising.

http://web.triton.net/r/rlgunn/

Other businesses request that the quill be removed with the spindle, and that those together be sent in for the re-grinding and, if necessary, bearing replacement.

I find the latter interesting since the Bridgeport service manual discourages removing the quill from its matched housing.

Logically one should expect a re-grinding to be necessary, after bearing replacement, if Bridgeport bought generic bearings, matched them, etc. and then ground the spindle seat in-place as a manufacturing process. As I read it one reply in this thread says this or the equivalent is the case.

In principle, it should be possible to install highly precise bearings, re-grind in-place or at least in the quill, and from then on replace those same bearings, if necessary, without the re-grind.

I recently purchased a Boss 5 Bridgeport on E-Bay. To my surprise I found the TIR of the spindle taper seat to be excessive. The center of the taper is .00075" off from the center of rotation. This shows a total movement of twice that on the indicator, or .0015", which I take to be excessive. However, the bearings are quiet and tight, and the taper seat undistorted. This combination has been a mystery to me (I am new to this and a hobbyist). From the contents of this thread I suspect a previous owner replaced the spindle bearings, apparently with good ones, without re-grinding the taper.

There are companies that sell bearing kits for these machines, as well as head rebuild kits. One of those is the following company that advertises its spindle rebuild kit on E-Bay:


http://cgi.ebay.com/Spindle-Rebuild-...QQcmdZViewItem

I have not decided what to do with my spindle yet, but I will do something. I have even considered getting the stuff to regrind it in place on my own machine. For one thing, I am not clear as to whether I should replace the bearings and re-grind the taper.

The statement that ice and heat should judiciously be used rather than a press, earlier, I found quite interesting.

I am new to this, as is the original poster. I read the service manual and am not clear exactly what the procedure in the manual means when it gives spindle removal instructions. I found the set screw in the quill, but I am not clear where the hammer blows are suppsed to be applied to remove the spindle with bearings (provided I decide to replace the bearings before the re-grind, and don't get someone to do it for me, etc.).

My inclination is to leave quiet and tight bearings well enough alone and just have the taper re-ground, even though I am not sure of the quality of the bearings in there.

Thanks,
Karl