Want to hang from v2xt

[v488]

I want to hang myself from my v2vt. I can't get any precision from it. I bought it from a junk auction. I've worked on it off and on for the last 3 years. The ways are perfect, no holes drilled in table and paint is cherry! It was used for heavy drilling and no milling. The head was to laud to even stand in front of when running. I sent the spindle to BOB at C&M Precision spindle for rebuilding. For $750.00 i got CHINA bearings, top & bottom with .0007" total run out! The milled finish was horrable!!!! After getting run around from BOB i knew i was on my own. Less $750.00. When the spindle was out i replaced ALL bearing in the head with USA or Japan brand name bearings. After spending a truck load of money for the bearings i found out that the local bearing dealer was screwing me. I did not want to deal with bridgeport becaulse of there high cost but i ended up paying half again more than bridgeports bearing prices !!! I also replaced the lead screw bearings and all 3 axis drive belts.
All this work and money got me was a Rebuilt " P O S " . In a fit of RAGE i called Bridgeport and got the correct spindle bearings. I pulled the CHINA bearing and replaced with the factory bridgeport bearings. Yes, i found all high spots like the " pros " do. I took a cut with it and it was ****! .0007 total run out. I had a spare Quill so i put spindle in the quill and sent it to Wells-Index to regrind the taper to run with the new bearings. When i got it back i put a indicator on the end mill shank and it was reading .0015 total run out after i put it back into the v2xt quill. The finish was ****!!!
Am i missing something here? I'm on a Mission to get this thing right! My money is spent! What does a man need to do to get near 0 run out? Is the run out caulsing the terrable finish? After spending all this money & time i could have bought a complete NEW spindle from bridgeport!
There was no backup disk with the mill. When i mill a circle it is way out of round, very large flats and .005 wall blend missmatch at lead in/out. The jibbs are tight , probley to tight. How do i adjust jibbs when you can't get a feel for the drag becaulse theres no handles. Could the backlash count in the controller need adjusted? How is this done.
Please HELP. Thanks Mike

[arsenix]

Do you have the service manual? It has the procedure for adjusting the gibs. At least my on machine (R2E4 Series II) you put an indicator about 12" from the center of the machine and push on the table. They give a figure for the max deflection you should be able to see. Unfortunately I don't have the manual in front of me to quote the exact figure, but I think it was a few thou.

If you can't mill a circle sounds like you have a backlash adjustment problem. The manual also says how to do this...

James

[NEATman]

Mike-
I too have a V2XT, but I have never had trouble with the bearings. I'll be gentle to my machine after hearing what you have gone through!

How is the surface finish bad? Is it rough, cupped, angled? Is the head trammed to the table? How are you measuring the spindle? Is the problem not the bearings but the fit of the OD of the quill in the housing of the head? This may be the case if the machine was used to do mostly drilling, especially if the did "pecking" cycles to clear the drill of chips. I'm not sure if that can be fixed - but there must be a way.

There is a group on Yahoo that is for V2XT owners. You can find the software there and even a PDF of the manual.

Also, there is a member here who is a lifesaver for bridgeport owners - I believe his screen name is Machinetek. I'll bet he'll respond to this thread also.

I hope this helps.

NEATman
Keith

[InspirationTool]

Mike, I have never run a V2XT, but here are my thoughts...

First of all, if you are having a rough finish, you need to tell us exactly what you are doing, and exactly what you are seeing.

What material, what bit, what RPM, what depth of cut, what feed rate? Climb or conventional cut? Is the quill all the way in or out? What tool holder?

Run out should have very little to do with a rough finish. It could be the difference between a nice finish and a really nice finish though.

If you have lots of backlash and you are climb milling, that could be a big issue. Have you checked tram?

Not sure about the way tightness... that should be in the manual.

-Jeff

[NC Cams]

A lot of the "aftermarket" bearings are pizz poor copies of the OEM Bridgeport bearings AT BEST. How do I know? I did machine tool bearing engineering for a noted machine tool bearing manufacturer for a number of years and BPT was a client I did work for.

Since I had and do have access to many of the OEM Bridgeport bearings blueprint specs, I know for a fact that many aftermarket bearings being offered are NOT factory equivalent.

Example: the OEM bridgeport bearings came with over and/or undersized OD's and ID's. They then selectively fit the bearings to the spindles/quills to "fit" the bearings and selectively fit them to get the precision. Hence, if you slip in some off the shelf bearings, you can't/won't necessarily get the proper runouts or fits. Period, Paragraph.

If, however, the spindle was nominally sized (chromd and ground standard if undersized or ground down to standard size if oversize) and the nominal sized, true ABEC 7 /ISO P4 bearing was installed in the spindle, you should EASILY get runouts under 0.0005", perhaps even near 0.0001" if the spindle was ID ground PROPERLY after the bearings were R&R'd properly.

I'm not going to bad mouth ANYBODY"s work. However, Simply R&R"ing bearings in a Bridgeport spindle will NOT necessarily guarantee you a proper rebuild. THe few ex-BPT guys who built spindles KNOW that what I"m saying is true!!!!

Chances are, the finish problems are due to spindle runout issues. With proper bearing fits and true running tools, you WILL have good finishes and proper sizes.

The out of round circles are caused by backlash in the ball screws and/or gibb slop and/or notoriously poor rigidity in the poor excuses for ball screw support bearings that the factory uses.

Do an Extrak search on this website and I outline in one of the posts how to make a Eztrak (same as a V2XT) machine deadly round circles via the use of properly preloaded angular contact bearings and properly adjusted gibbs. BTW, you can't fix sloppy a$$ worn gibbs via adjustments - they have to be refinished.

Unless you can find a sharp guy who KNOWS how to engineer bearings, simple machine tool service people are only capable of R&R'ing off the shelf generic bearings which, unless they are properly engineered in the first place, can't won't fix your problems.

We know how to do it - engineer and fit bearings - we did it on our machines (Extrak and V2XT). Some of the fixes take knowlege, some take $$$'s and some take time and experimentation.

Howe good do you want it to be and how much time and money are you willing to spend?????

[NC Cams]

By the way, some of the selective fit bearings that were used in the early generation Bridgeport mills, V2ZT's and/or Extraks aren't made anymore.

Hence, even if you bought Hardinge/Bridgeport bearings, that doesn't guarantee that you'll get the same size coded pieces you originally had in your machine to begin with!!!! I'd say that the runouts you'r reporting are proof of that.

Regardless, once the bearings are replaced with TRUE ABEC 7 variants and the spindle taper PROPERLY reground to run true to the axis established by the bearings, you should have dead nuts tool runouts. if not, somebody did something wrong or something else is wrong with collets, tooling, something.

[machintek]

You said this did a lot of drilling. What is the play between the quill and the housing? Are you keeping the knee locked?
I have sent many spindles to C & M for about 16 years now and was never disappointed. But anyone can make a mistake.
How are you checking this? They typically have a fixture and grind the inside of the taper with bearings installed so there is no run out.
Is your spindle bent?
Is the head floated in? (so the splined gear hub is not applying side forces on the spindle shaft).
Is the quill nut on the bottom pressing against the bearing outer races or is it bottomed out on the quill?
There can be many places where you can get runout from.

George

[v488]

Thanks to everybody for responding!
I want to tell you about C&M Spindle and Mr. BOB. He went on and on about how C&M Spindle was going to be the greatest thing that could happen to my spindle. Cost was $750.00 + shipping. This got me NEW Bearings & NMTB30 Regrind. I was told to build a wooden crate to ship spindle in to protect it and it would be sent back in my crate. I built a box so nice i thought about putting some stain on the wood and French Polishing it! The box was Over built! I sent it out , Bob did his thing and sent it back in a Cardboard Box!! What the Hay!! I opened the box and pulled my " baby " or spindle out to take a close look at it. I set it up on its snout on the table and seen where someone took a die grinder and ground off the word CHINA on the outer bearing race and even ground CHINA off the RUBBER SEAL!!!! There was grit from the grinding in the gaps of the seal. How clean is that! How did i know it said CHINA if it has ground off ? Well Bob did not grind deep enough to wipe out the word CHINA. DAAAURRR!! I could still see CHINA on his ground up rubber seal! I called Bob and asked him about his die grinding work. He told me " I have to grind off the information from the bearing so other shops won't find out where i'm getting my parts " and " Thay are the BEST BEARINGS in the WORLD ! " Well if Bob did not want other competators finding out where he gets his " Best Bearings in the World " why did he NOT Also grind off the 10 digit PART # !!
Well the next day while the spindle was sitting on the table on its snout upright, i was turning the " Best Bearings in the World " with my finger tips and felt lots of GRIT rolling around inside. Than the Bearings grabed a big pice of GRIT and instead of only the Bearings turning the Hole Assembley turned. With the weight of a complete spindle assembly sitting up on end on the table and my hand turning the outter race of the bearings , THE HOLE SPINDLE ASSEMBLY TURNED ON TOP OF THE TABLE !! I called Bob about this and he said " It is only the end cap rubbing the bearings no problem ".
Bob did say to send it back and he would look at it. Now i was a man stuck between a rock and a hard place! I had so many things needing to be milled i was SICK !! My father said the best thing to do was to run the mill with the spindle as is and hope for the best. The Best NEVER HAPPEND! The finish was horrable. .0007 total run out indicated inside NMTB30 Bore. This made it
.0015 TIR at tool. Thanks Mike

[gus]

A lot has been going on about bearing sizing etc. I am no expert, but I looked up ABEC 7 bearing specs, and it looks to me like standard is around .00015 max deviation in diameter and runout.

There are others that know better than I, but I imagine, as in automotive manufacture, the grading of the bearings is for assembly in manufacturing. Statistically, your bearings should deviate no more than .000075 from what you have, although it could be the max .00015, it is unlikely. If the dots are lined up in matched pairs, then the two should rotate creating a cylinder shaped error, if they are not lined up they might create a cone shaped error, increasing in size with distance from the bottom bearing.

One 'should' be able to properly install a good set of ABEC 7 bearings and see very good results. Bridgeports are NOT a super accurate machine. They are not a jig borer. If one reground the spindle taper with the bearings installed, it ought to be better than new, down into the accuracy of the grinding machine.

[NC Cams]

You didn't indicate which OEM bearing numbers you replaced buy I'll make some assumptions to help you get going.

If the lower bearings are the OEM #11190238 the EXACT Fafnir OEM equivalents to the Bridgeport pieces are/were JM207PRDB FA52727 - anything and I do mean ANYTHING else is NOT an exact equivalent.

These SHOULD come with OD/ID high point markings AND over/undersize marking of the ID's and OD's in 0.0001" increments so as to enable you to selectively fit them to the housing or shafts. They are a special combination ABEC3/ABEC 7 hybrid bearing that Bridgeport conjured up way back when.

IF the "worlds finest" bearings don't have these special qualifiers as well as a special preload and some other special internal features,you got a generic part that is NOT of an OEM equivalency - I know of what I speak since I have the OEM print for these very bearings sitting in front of me as I type this reply.

There are some other specs involved qith these gems but nothing that I'd care to publish since a user couldn't do anything about meeting or getting them if they had to/wanted to.

If you want a high performance bearing "upgrade", you could try the 7207CTYDUMPA7 or 7207CTYDUMP4 true machine tool grade bearings from NSK. These are FULL ABEC 7 and have touch more preload than the OEM spec but nothing signifigant. You'd never know the difference when they are properly installed except that they should turn smooth as glass and have no appreciable runout.

NOTE: The NSK's do not have the shield/seals that the Bridgeport bearings used but that shouldn't be an issue as the housing is sealed up pretty well and the seals on the bearings are not mandatory if that is the case. If you use these, you MUST check and grind the 12193513 spacers to be exactly the same axial length - some spacers may be unequal length to tweak preload. Grease lube the bearings with a 25% fill of "Andok C" (Chevron makes it I think) bearing grease (the exact OEM grease) and you'll should be good to go.

In either case, once you install the bearings, the spindle ID's will need to be ground to bring the axis of the spindle back to being concentric with the axis of the bearings. Having been at Hardinge a number of years ago and seen the process, this is EXACTLY what they do when they service and/or build/rebuild a Bridgeport mill spindle.

Where you'll find a reputabe shop to do this is probably your hardest find, especially in light of your experiences to date.

Rough turning "new" bearings were probably either damaged at/during installation and/or were lubed with contaminated grease. Running in rough bearings hoping that it "heals itself" is worse than wishful thinking - I'd contend that it is just plain dumb.

The 11190237 upper bearing is EXACTLY a M206K Fafnir. Again, anything but is a generic "equivalent". I'm pretty sure, but from memory, that the M suffix of the Fafnir means that the bearing is specially qualifed to at least ABEC 3/ ISO P6 for machine tool use - it may have other special specs, special lube and/or other non-standard, non-published features but I don't have the OEM bearing print to confirm that. Again, anyting BUT is NOT the exact equivalent.

Re: bearing installation. You can press the old ones off/out but NEVER, EVER use force (hammers, presses, pullers, etc) to install the new ones. If you Freeze the spindle and heat the bearings, they should literally drop together. When the temp normalizes, the parts should remain tight. If the bearings are loose when temp normalized, congratulations, you have a funky sized housing/shaft and need the selective sized bearings that were originally used that you'll probably never find anymore.

The alternative: chrome and rr-grind the shaft to standard size to obtain proper fit.

It is NOT that hard to replace spindle bearings without damaging them if you take time and do it properly. The trouble is, some guys want to rush or slam stuff together. In other instances, familiarity breeds contempt and or sloppy procedures. You seem to have been a victim of one of these methods - I'll bet you can figure out which by now.

You might give Brian at BPT Machines a call. He was a true factory technician and knows of several "old timers" who originally built the Bridgeport spindles before Bridgeport went belly up and still service them. Perhaps he can put you in touch with someone who can straighten out what you have. Call him at 630-984-9942

Good luck

[9 1/2]

Man, here I sit eagerly awaiting delivery of my V2XT, and reading all this stuff is both enlightening and worrying.

I sure hope the machine tool fairies are on my side ............

[NC Cams]

Memo to 9.5: if your machine is in decent shape and still has the factory stuff and has NOT been "improved upon" by a well intended but ill equipped techician, you should not have much to worry about.

Anytime you start letting non-factory people work on machine tools, you'll never know if they KNOW what they're doing or are simply using your machine for OJT (on the job training).

There are people out there who KNOW how to service BPT's. THere are folks out there who THINK they know how to service BPT's. There are folks with skills anywhere's inbetween.

How you find the experts takes luck and, perhaps, a lot of phoning to check up on so-called experts. Any technician should be happy to provide you with references. Naturally, they won't give you the bad ones. HOwever, if you ask around to other shops, you just might find a common consesus.

WE did exactly that with some trick heat treat sources that we needed and had real good results. We also went an interviewed the place BEFORE we sent the stuff there. Clean, well lit shops tend to do good work. Shops that look like they are a dungeon and walk around with grimey greasey clothes generally do not do brain surgery-like work.

References, multiple in some instances, are always prudent to check out and/or verify.

I sure hope V488 used a credit card to pay for his spindle rework. The credit card company can apply some "leverage" when prompted (as in holding up payment) if the customer is unsatisfied with the work/service.