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.

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

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

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.

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.

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.

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.

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.

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.

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>

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.

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-Kit-for-Bridgeport-Series-I-Mill_W0QQitemZ7618021332QQihZ017QQcategoryZ25290QQcmdZViewItem

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

Selective fitting is why:

"the Bridgeport service manual discourages removing the quill from its matched housing."

Hammers (shudder) can be used to remove bearings but all thread rod and some sleeves and arbor adapters will do it just as well without being primitive or crude.

The 0.0015 TIR was probably the result of "junk bearings" that the guy bought someplace. Seriously, probably R&R bearings, didn't grind taper, oh well... Knowing what the OEM bearings were and how they were fit, it doesn't surprise me.

Re: ice and heat = while at the machine tool lab of my former employer in Japan, they showed me how to reassemble ANY spindle without a hammer or even a press anywhere's nearby. Between freezers and electric skillet/hot plates, they assembled spindles and the bearings literally FELL into place.

We used the pop freezer, heat lamps and a propane torch to heat the housing/frerze the bearings for our cam grinding spindle in the previous bearing R&R deal. The thing literally fell together with the proper thermal differentials.

WE even screwed up and put the R bearing on the L side - the folks who sold us the machine said we'd have to buy a new bearing ($425 each) as they'd never seen one removed without trashing it.

Not only did we remove it once, but did so a second time when we had to add 0.0003" chrome plate to OD to tighten up the clearance a bit (it is a 'precision' bored bronze bushing)- all thread rod plus some tools, 5 minute job. Hint: put a roller thurs washer under the nut on the rod, it turns MUCH easier.

Think before you act. The shop freezer and a $3 electric skillet (has a temp knob) from the recycle place (teflon coated no less - we spared NO expense) form our "precision thermal fit bearing istallation system". After all, there is a knob with degress marked on the skillet control knob!!!

Heat bearing, freeze spindle, it should drop together. Freeze assembly, heat housing, you should be able to slip it together with NO hammer or press force whatsoever.

Hope this helps...

I really appreciate the information.

Your guess that the TIR is from junk bearings makes me want to replace them, but that sentence about adding chrome to the bearing speakes to what scares me the most about changing the bearings. The press fit on the spindle should go on absolutely tight, when at the same temperature as you point out, but the fit into the quill must on the one hand slip in, but nevertheless be loose enough to install and remove. Any bearing I buy could miss on that, it seems.

The addition of the chrome, is that a straightforward process and does it require grinding after?

Thanks,
Karl

NC, I'm trying to understand the selective fitting part, I gather its creating a small tolerance situation by manually selecting pairs within the wider variance of a large tolerance set of pieces, ie just keep trying until we have two that are ___.

What I'm not sure of though is what parts are being matched and to what objective. Is it the ID of bearing to spindle OD for example? If the tolerance is controlled by this manual matching, but then presumably the nominal size could wander, for instance instead of a being + .0001 tolerance on 2.0000 inches, its say +.0001 on 2.0004 inches - still a +.0001 tolerance so performance is there, but when the bearings are replaced, how do you find one for a 2.0003 shaft? or am I not understanding what is meant by matching.

Secondly, if the spindle is made with the od concentric to the taper, how does the installation of bearings push it out over a thou? The bearings as you described a light interference fit so are they not perfectly concentric with the shaft? where does this error come from - can the bearings be that far out ?!?

karlden: the "junk bearing" comment was a tongue in chieek reference to the "junk bearing comment in an earlier post.

Here's the size matching deal in a nutshell: If you have poor size control of spindle OD and housing ID, you need oversize/undersize bearings to compensate. So, instead of holding GOOD size control of the bearings, they'd simply run them and then selectively size code them. The assembler could then mix and match as the situation arrised. I've seen size ranges of as many as 6 ID and OD ranges, all mixed and matched. ABEC 1 bearings allowed in the old days, a decent range of size shift so this was possible.

You'd match a big ID bearing to a large OD spindle and vice versa, you know match them to achieve the desired press because you didn't/couldn't maintain size control at the time. This method went to heck real quick when SPC got implemented and bearing size control got DEADLY consistant/accurate, and at no cost penalyy to the customer.

How do you find one for a 2.0003 shaft?? SImple, wait until you find a bearing with a bore ID 0.0003 too big. Like the process suggests, selective matching of sizes.

Re: eccentricity = the older bearings in the day had much higher eccentricity runout allowed (spin the inner ring and measure the ID of the bore runout0- it still is allowed but improved QC makes them low runout no matter what - even ABEC 1's.

Anyway, in the 'old days' they'd have the bearing eccentricity high points marked on individually sorted ABEC 1's which were allowably sloppy for the day. They'd do the same for the spindle taper to journal OD.

You would then mount the eccentricity high point OPPOSITE one another to bring the spindle taper coaxial to the center of rotation of the bearing. Selective fit accuracy as opposed to grind/make it right accuracy.

Naturally, you needed quantified and marked values to mix and match as need be to get stuff to work. In some cases, you could actually mix n match to the point where you didn't have to grind the ID taper - maybe after going thru 4-5 bearing sets but they were cheap even with all the pedigree work - and cheaper than grinding.

Sadly, you needed 5-6 times the amount of bearings to service all the permutations of junk you were trying to make do into "precision machine tools".

The problem was that as bearing quality improved, and/or a person later on unknowingly simply slipped in new unmatched bearings, the NET assembled TIR of the spindle taper went to heck in a hurry. Since the only thing that was replaced was the bearings, obviously "the bearings were junk". NOT HARDLY!!!!

If your machine is from the "select fit days", you can probably bet that a bearing R&R will not result in low taper runout. Even the ABEC 1 stuff is so good anymore that it isn't that hard to inspect and find ABEC 7's - until you do the runout check - that's where 1's fall short big time of ABEC 5's or 7"s. Check it out and it is easy to see how you can add or subtract runout accuracy by stacking tolerances in both directions. AND yes, in the old days, they could be thaf far out, especially if you ORDERED THEM THAT WAY.

Check out the bearing handbooks for the inner ring radial runout allowances for 1 vs 5 vs 7's. Where do you think the ones that don't quite meet specs just might get dumped??? Been roller skating or skate boarding lately????

I'm not telling you to chrome plate anything - please re-read the post. I had to chrome a bushing OD to snug up the bearing clearance due to a pizz poor size that was bored too big in the "precision bored" bushing we were installing into our cam grinder. Plating the OD of the bushing reduce ID size and net clearance what we need to shrink it.

EDIT

If we're talking spindle, find some ABEC 5's or 7's in the appropriate size.

Check to see if spindle OD size is within specs for the bearings you're using.

Make sure they're properly preloaded (DUL or DUM should suffice) - they used generic ABEC 1's and made the spacers odd ball lengths to get the preload needed - DO NOT SIMPLY R&R ANY SPACERS YOU FIND!!!!

Make sure they're equall lenght spacers if you use aftermarket preloaded machine tool A/C bearings.

After installation (via thermal fit methods already outlined) plan to have ID taper reground.

The thing will run as good , probably better, than new if you do it this way for longer than you'll probably live.

That pretty much does it.

END EDIT

How do you find one for a 2.0003 shaft?? Simple, wait until you find a bearing with a bore ID 0.0003 too big. Like the process suggests, selective matching of sizes.




thanks for expanding on the process, lots there i didn't know and appreciate the insight of one who's been there - hopefully you don't tire of the plebe questions.

on the hypothetical 2.0003 shaft Q, I was more wondering what happens now if you are replacing the bearings - a better example would be 1.9997 spindle/shaft as "grind to size" isn't an option. The replacement bearings are going to come with a nominal 2.0000 dim (ok, should have picked a metric example) and are not going to fit the shaft properly.

so how does a spindle repair shop, working with one of these from the "select fit days", do the bearing manufactures/suppliers sift through lower grade/higher variance bearings looking for a 1.9997 bearing, are they custom ground, or something else?

How do you compensate for a 1.9997 shaft in service?

Simple fix:

Flash chrome plate - 0.0003" is a no brainer

But you then still have to ID grind.

More complex but nets out to less work if done well:

Grind 0.005" u/s and them build back up with 0.008" chrome. Grind OD to proper size BUT use an arbor on the ID and thus "fix" the initial ID taper runout at same time. This should make any future R&R a no brainer (and it keeps the ID taper a standard size).

If the inside race (the one that revolves with the spindle), were such that the center of the circle defined by the bearing surface were off by 0.00075" relative to the center of the circle defined by the the interference fit surface (against the spindle), then the TIR would be double that, or 0.0015" (as I understand the definition of TIR, again I am new to this). The outside race that is stationary against the quill would not have this effect, but other issues could obtain from inaccuracies in that race.

Because the inside race is stationary with respect to the spindle, re-grinding the taper can compensate for concentricity variance in that part of the bearing. However, if such a compensated bearing were replaced (or even removed and re-installed at a different rotational position), then a re-grinding would be necessary to make the taper concentric with the rotation of the spindle. This would occur even if the new bearing were perfect, since the taper would have been previously ground to compensate for the removed bearing. This last effect is one thing that NC Cams may have been talking about when he mentioned that people blame good new bearings for poorly performing machines.

NC Cams replied while I was writing this, thanks for the info on the use of chrome to adjust a bearing.

Karl

Karl: instead of trying to mentally understand/redefine what's going on with respect to runout, go to the NSK website, download the bearing handbook and read/comprehend the section on "Bearing Tolerances".

Bearing tolerances are all specified in easy to understand, intenationally recognized standized terms.

Runout depends if you are working wth inner ring or outer ring rotation. The runout of the ID or OD with respect to the raceway is defined puraunt to bore size and ABEC/ISO accuracy ratings.

Yes, "junk bearings" are the result of cumulative SYSTEM runout that is spindle feature based but bearing identified/blamed, and usually incorrectly so.

Now I am really confused..................... I got a guy comming over Saturday to fix my mill. I hope that in a few days it will be fixed right, and at a fair price. Then I will have answered my own question and will post his name and number for all to use that are the same situation that I was in.

New to this or any machining forum for that matter, and I thought this would be a quick and easy question to answer.

Thought wrong though!

Thanks anyway
Steve

Steve: I'll make it real simple:

If the guy "fixes" your spindle by sticking in a fresh set of bearings and doesn't

1. Check spindle taper runout
2. fix it if it by grinding in place if it is over say, 0.0005" TIR

He didn't fix your mill.

In lieu of what factory did back back when yours was built to selectively fit and assemble spindles with the procedures/parts available to them at the time, you ain't gonna fix it today by simply swapping parts.

If you're lucky, yes but don't count on it.

BTW, if you see the guy take out a hammar and a prick punch to start "fixing" the spindle, tell him to put his "tools" down and leave. Butchers use prick punches to "fix" the spindles instead of plating and grinding them back to true size.

I wouldn't fix a drill press with a prick punch, let alone a Bridgeport mill. A well serviced Bridgeport will hold tolerance for several lifetimes of service. A butchered one is hardly worth its weight in scrap.

Precision machine tools are not useally fixed with simple and easy fixes. This is why GOOD ones are so costly.

Hand massaging done in a PROPER fashion is beyond costly, it is downright wince in pain expensive.

Learning the "factory assembly secrets" so you can DIY on a FREE message board, PRICELESS!!!

NC Cams,

Thanks for the input. I guess I used the word "guy" loosely. This person is the machine rebuilder for a friend of mines high end machine shop. I didn't want to impose on the friend so I thought I would put some feelers out on my own on this page and see what the response was. With the response I got I made the decision to impose (what are friends for) and ask if his rebuilder would fix mine. So I feel that I am in good hands.

Thanks anyway
Jangaard

Kool

Anyway, you'll still know what to look for - and since you do, you'll impress the guy to no end with your newfound knowledge.

Pay attention to what he does and how he does it. It may come in handy some day.