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Benji
05-09-2004, 08:20 AM
I have an interest in what all the bearing numbers(spindle,pullys etc) are in the "J" head circa mid 60's....I put a querry out awhile back on the Bport reflector and only had a 1 reply from someone willing to sell me their bearings....I would like to know the manufacturers (Fafnir,FAG,NSK,SKF,Etc..) numbers..NOT the Bport numbers......I can get the bearings thru work at or near cost (or free if they are on the shelf and obsolete) and want to have a set on hand in case I find time to wanna put them in..(not that it needs it)...without tearing it apart first to get the numbers...and then wait for the bearings....It lookls like there are 9 bearings in all?...I just rebuilt the motor so I wont need these numbers...Also wondered for the home shop guy is the class 7 bearings necessary?..or could one get by with class 5?..

So please if anyone has this info I would surely appreciate it!...

Thanks,

Mike
Niagara Falls NY

Spin Doctor
05-09-2004, 08:51 AM
Just measure up the bearing IDs, ODs and widths and compare to a bearing catalog. I'm sure there have to be some on line. The one thing that has always ticked me off with the bearing manufactures is they always used differnt suffixes for the codes for seals, shields and snap rings.

A link to the SKF on line catalog

http://www.skf.com/portal/skf/home/products?paf_dm=shared&paf_gm=content&paf_gear_id=4400006maincatalogue=1&lang=en&newlink=1_1_1

[This message has been edited by Spin Doctor (edited 05-09-2004).]

Charles Ping
05-09-2004, 10:20 AM
I've been thru' this and used Class 5 bearings in the quill. Greater minds than mine have argued about replacing 7's with 5's on one of the workshop sites but I've had no trouble - however I'm a light user!

The bearings that I took out, which may not have been original had no seals so I left them off when I replaced them. The BP lubrication is drip/total loss so it made sense to me.
The base were 6207's and the upper quill bearing was a 6206 - all standard bearings in ABEC5.
I don't have the spec for the ones in the top housing with the back gear but they were standard precision (not ABEC5).

Regards


Charles

John Stevenson
05-09-2004, 11:52 AM
Mike,
Just go for it.
Never been one to be outspoken http://bbs.homeshopmachinist.net//biggrin.gif but I have had this argument many times.

When Bridgeports designed the J head back in 1950, although it wasn't released until 1952, they specified an opposed matching pair of ABEC 7 bearings which were the best they could get up until this point.
The M head never had these.

So in 1952 they used these quality Grade 7 bearings and everybody was happy.
Since then, and the bearing people have the specs to prove this, bearing quality has risen dramatically.
It's now got to the point where class 5's are half as good again as the ORIGINAL specified class 7's that everyone was happy with at the time.
True class 7's have also risen but are now to a greater spec than original.
So all you purist's out here fitting modern class 7's either swap them for 5's or find some old class 7's http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif you are knackering the ORIGINAL spec up http://bbs.homeshopmachinist.net//biggrin.gif

Modern class 7's are an improvement but the only people to see this are toolmakers running loooong jobs at high spindle speeds, no one else gets the benefit of the extra quality.

There were approximatly 26,000 M head machines made but no record was ever kept on spare heads sold to other manufactures or even fitted to twin and three head machines.
So if we say 27,000 M heads produced on standard bearings of the day if there had been a problem do you think they would have kept their reputation.??

A second item to take into concideration is that unless class 7's are fitted correctly they will only function as good as a standard bearing, so all that extra quality and price is wasted anyway.

I'm bound to get flack for this but I'm sticking by my guns when I say that NO home shop guy will be able to tell the difference between class 7's and 5's if fitted correctly.

Think about this for a minute, you have an original Bridgy, fitted with class 7's in good condition, never touched but it's now 30 years old.
To what extent have the bearings degraded so that although still more than servicable they are actually worse than new class 5's.
At some point in it's life, before any play develops these bearings will have worm past class 5 spec.

My God guys you better get out there and rip those spindles apart or you won't sleep nights http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

John S.

Spin Doctor
05-09-2004, 12:20 PM
The only way the average HSM is going to get the full advantage of class 7s is if they can properly fit the spacers and properly inspect the spindle arbor itself. But in the end you've still got the upper end rattling around in a radial bearing any way. One thing we have done with some of our BPs at work is when the head has to be rebuilt we use all sealed bearing in the upper head and varidrive assembly. On the lower spindle bearings we will refit the spacer s so as to allow the use of a set of three angular contact bearings with the bottom two mounted in tandem with the upper one back to back. For the average HSM I would not recomend his trying this as the spacers have to be absolutely right. When ever I grind bearing spacers I always grind them on magnetic parallels that have been ground on the surface grinder and not removed from the magnetic chuck prior to grinding the spacers. This means that you have to grind the parallels each and every time but that is what they are for. To provide a scraficial surface that you know is going to be absolutely the flatest the grinder can be. Also coolant is vital to control part growth. I am usually aboe to hold spacer flatness to under .00005" in this manners. Also the grease used in the precision bearings will have a great deal to do with their lifespan. Personally I would recomend either Kluber NBU15 or Anacol. They are available from Barden under the #s G46 and G75 in 30cc syringes at about 15 t 18 bucks a syringe. At the cost of the bearing assembly don't scrimp on the grease used. Plus the syringes come with a fact sheet on the proper amount of grease to use in each bearing size. Additionally the bearing stack should be checked for run out after it is installed on the shaft and locked in place with the bearing retaining nut. This can be checked by hoding the shaft in a dismounted lathe chuck and rotating the bearing assembly with an indicator on the side of the top outer race. Any runout can be "tuned" out buy tapping on the nut with a soft piece of steel and a hammer. It is not the fitting procdedure that is causing the runout but the nut itself

docsteve66
05-09-2004, 03:27 PM
I agree John, "A second item to take into consideration is that unless class 7's are fitted correctly they will only function as good as a standard bearing, so all that extra quality and price is wasted anyway."

#5 years ago I attended a bearing symposium, chaired by a one legged pilot who flew for Germany in WWll. According to him, precision bearings are factory mated and marked. Unless the marks are lined on both sides , the bearings will perform no betterthan a bearing of the next lower grade. It's all no relevant since most bearings suffer damage being installed.

Greases? For critical aircraft bearings, we weighed the grease packed into each bearing. There was a surprisingly small number of different greases involved.

Mr Bridgeport
05-09-2004, 05:43 PM
Hi Mike, since nobody has answered your question, I'll post what I found from my old copy of Fafnirs Machine Tool Bearing Interchange manual. For some reason it didn't have the numbers for the class 7 spindle bearings. If I find my latest copy, I'll check it. Fafnir was used a lot in the older Bridgeports.
Top spindle bearing, Bpt PN 11192037, Fafnir PN M206K-E6578
Spindle sleeve bearings, Bpt PN 11190232, Fafnir PN RM207PP-DB-E8681
Gear hub bearings, Bpr PN 11190230, Fafnir PN RM208K-DB-E8681
Backgear pinion bearings, Bpt PN 11180235, Fafnir PN 203NPP-C8-FS59147.
I would use class 7 bearings for the spindle and carefully install them. Line up the runout witness marks on both the inner and outter races. You won't damage the bearings as someone stated if you heat the bearings up to about 200 degrees F, they will slide right on. I've done this many times useing an old hot plate with a clean piece of aluminum plate on top. Use a thermocouple to check the temp. Use a fine india stone to check for burrs on the faces of the inner and outter bearing spacers. Once the nut is tightened, check the outter spacer for runout and tap it to run true. A spindle rebuilt in this manner will usually have less than 0.0002 runout measured on the taper if it wasn't damage before hand. Good luck,, Bill

Spin Doctor
05-09-2004, 05:50 PM
Doc, if bearings are damaged during installation it is always due to the lack of knowledge on the part of the installer. Bluntly put they don't have a clue as to what they are doing. Most spindle bearings should be either heated with a bearing heater (135D is usually sufficent) or pressed on by a mechanical means that puts equal force on the inner and outer races at the same time to avoid impact events transfered from one race to the other through the balls. Plus one thing that should alays be done with a precision rotating group is to run the spindle in from a slow speed (25%) up to the full operating speed keeping an eye on heat.
If I get the chance tommorow I'll post some j-pegs on Photobucket of the types of appropriate tools to use if the bearings must be driven in by means of a hammer

coles-webb
05-09-2004, 06:04 PM
NTN has a good site with rights and wrongs for bearing installation.

http://www.ntnamerica.com/Engineering/PDFs/Other/9102cat.pdf

Mike

Benji
05-10-2004, 09:45 PM
Thanks for the replies and info...I hope to obtain some bearings to keep on the shelf for that "round tuit" I keep trying to find..Appreciate it guys...Mr Bridgeport...I will keep you in mind for any future info if thats OK with you?.Tks agn..

Mike
Niagara Falls NY

wierdscience
05-10-2004, 10:10 PM
Screw the angular contact balls,I have retroed two J heads with Timkem precsion tapered rollers,all it requires is to make two new spacers.

The benifits are two #1 Much higher load capacity and life

#2 They are cheaper

Add to that most J heads don't turn up more than 2800 tops.Both pair I have changed are still going strong with rock solid runout.

If you want to stick with the balls and can't find any,we have some class 7's at work I can get cheap,just shoot me some diems or numbers and I'll see what we got.BTW the ones I have are RHP,sold by the pair with the races marked for concentric.