Bridgeport Clone Spindle Bearings

[Allan Plant 1Participant @allanplant1]

Hi

I need to replace my spindle bearings on my Bridgeport (clone) mill, the bearings that have come out are SKF 7207 B, there's an A opposite, 72mm X 35mm X 17mm.

I've looked these up and there seems to be lots of different variations?

any help would be much appreciated.

many thanks

Allan

[Allan Plant 1Participant @allanplant1]

[David Clark 13Participant @davidclark13]

Talk to ARC Euro trade.

[FMESParticipant @fmes]

Try these people, I have no connection apart from being a well happy customer

**LINK**

We have used them on our Bridgeports

Lofty

[MuzzerParticipant @muzzer]

The clones seem to be metric whereas the original Bridgeport is US imperial from what I recall. The suffices indicate things like whether or not it has seal(s) etc.

You've probably seen something like this which says that the 7207 is 35x72x17mm and this which suggests that the -B part has a 40 degree contact angle. The A looks as if it may be a double row or possibly some other special condition.

Probably worth getting a known branded part for an application like this. If you weren't bothered about quality you could buy a bag full for a few quid off an auction site. I'd like to know where to get a decent (SKF?) replacement set, as I too have a (Taiwanese) BP clone.

I hope / expect JS will have some ideas….

[Bob Brown 1Participant @bobbrown1]

7207 ACD is an expensive high precision version 7072B is a more general engineering bearing, the latter in a SKF bearing are available here **LINK** but not limited to. Not all bearings even of the same size are equal.

Edited By Bob Brown 1 on 17/02/2015 19:21:05

[John Stevenson 1Participant @johnstevenson1]

OK my take on this and I know I'm going to get flack over this.

The Genuine Bridgeport bearings for UK made machines is 7207CTRDULP4 these are mega expensive ABEC 7 matched pairs.

Now bear in mind that this is an original 1952 design and I dare say these bearings were specified as being the best of the best for the time.

But, and this is where the flack comes in. If you have a genuine Bridgy with the proper bearings at some point down the line wear sets in and play develops eventually becoming enough to warrant a set of new even more expensive bearings as costs have moved on.

So for round figures we will say this thing is brand new and in a tool room and after say 12 – 15 years then play develops in the Abec 7's.

However until play develops the wear isn't noticeable as the bearing have degraded and what was an Abec 7 three years down the line is Abec 5 and 6 years down the line is Abec 3.

So if we as in home shop, non space shuttle mode, fit a set of standard 7207's to Abec 5 then we will have the equivalent of a three year old Bridgy with a proposed industrial working life of 12 to 15 years minus 3.

In home shop terms this is 17 generations of old fogies.

Now also take into account the imports produced over the years, true there have been good and bad but currently industry favours the Taiwanese clones over the Genuine Bridgy on a cost / suitability ratio.

I currently have the biggest clone sold in this country, the Warco WM40 which is basically a clone on steroids and will out cut and out shine a Bridgy any day of the week, so what does this have for spindle bearings ?

Just a set of branded 7207's. My machine is currently two years old and has probably done 8 to 10 years of hobby work and so far I don't have any problems, or see any problems.

Bearing quality has also risen by leaps and bounds and I dare say modern 5's are probably better than the 1952 7's

I seriously feel we can get too hung up on specs, what can be and what should be when in fact if we use the bloody thing we won't know the difference.

Majority of the hobby machines out there don't even have angular contact bearings, don't even have matched sets, don't even use then as a back to back arrangement with a top floater but instead just fit 2 generic deep groove ball races, one top, one bottom.

However then look at just what has been made on these machines. Jason if my memory serves has a generic X3, no fancy bearing in those.

Anyway please read, inwardly digest and I can assure you I have wide shoulders.

[Bob Brown 1Participant @bobbrown1]

I changed the angular contact bearings in my Dore Westbury as I prefer tapered roller bearings, fortunately they were a straight swop. My thinking is tapered roller are easier to adjust out wear and they are what are fitted to my bigger mill.

Bob

[Allan Plant 1Participant @allanplant1]

Thanks for your comments, I'll go with the SKF 7207 BEP's then, What grease should I use, might as well order some while I'm at it.

Allan

[MuzzerParticipant @muzzer]

These boys seem to be one of the main suppliers in the States for BP parts. It's helpful to know that "ABEC7" refers to the level of precision – I've learned something useful today!

The ABEC7 bearing kit seems to be $325 from them and there's a vid showing how to fit them. Can't say I'm massively impressed by the state of their workshop and their advice for setting the nut is "knock it pretty tight". Presumably that's a technical term. I love the way he "cleans" his hands at 4:55! I'm not convinced Ron Dennis would offer him a job.

All in all, it doesn't look too tricky if you can figure out how to drive the bearings on and off. I'd love to hear how you get on.

Murray

[Allan Plant 1Participant @allanplant1]

I watched that video and a few more, the spindle was easy to remove but the Allen bolt which holds the top of the quill stop had to be removed which I had seen on another video as it was stopping the spindle coming out. also the big nut was left hand thread.

Once out I knocked the shaft through all the bearings and spacers together with a nylon hammer, came out easy but will be using the press to re-install.

Allan

[Ketan SwaliParticipant @ketanswali79440]

Posted by Muzzer on 17/02/2015 23:30:42:

These boys seem to be one of the main suppliers in the States for BP parts. It's helpful to know that "ABEC7" refers to the level of precision – I've learned something useful today!

The ABEC7 bearing kit seems to be $325 from them and there's a vid showing how to fit them. Can't say I'm massively impressed by the state of their workshop and their advice for setting the nut is "knock it pretty tight". Presumably that's a technical term. I love the way he "cleans" his hands at 4:55! I'm not convinced Ron Dennis would offer him a job.

All in all, it doesn't look too tricky if you can figure out how to drive the bearings on and off. I'd love to hear how you get on.

Murray

Hi Murray,

Americans like ANSI, and Europeans like ISO. So, ANSI ABEC7 = ISO P4.

Most common contact angle for match pair super precision angular contact bearings is 15 Deg. which is designated by the letter 'C' after the bearing number.

So, if JS is correct about what was fitted to the original Bridgeport, '7207CTRDULP4', then the letter C in this code means 15 Deg. contact angle, DU = duplex matched pair, L = suitable for light preload, P4 = ABEC7 precision.

NACHI – JAPAN price for the match pair 7207CDUP4 = same as above reference number = RHP/NSK reference number for the above = or better than SKF quality….probably…, currently GBP115.00 including VAT, delivered U.K. Mainland for the NACHI brand.

In the super precision match pair world, SKF by brand is 'less regarded with desirability' than others….in our opinion.

Ketan at ARC

Edited for clarification of brands/quality, and price indication specifically for NACHI brand at time of writing.

Edited By Ketan Swali on 18/02/2015 12:04:04

Edited By Ketan Swali on 18/02/2015 12:06:38

[JasonBModerator @jasonb]

Yes John, 1997 vintage X3 no stripping or cleaning, just adjusted the two locknuts when delivered as they were loose and not touched since so still running the original chicken fat in the bearings and I have done some big models on it.

J

PS It was not an ARC supplied machine, I think they have tight nuts

[Ketan SwaliParticipant @ketanswali79440]

Posted by JasonB on 18/02/2015 12:46:05:

PS It was not an ARC supplied machine, I think they have tight nuts

Depends on how many times a machine is dropped in transit to determine how tight the nuts are

Ketan at ARC

Edited By Ketan Swali on 18/02/2015 13:07:22

[MuzzerParticipant @muzzer]

Ketan – thanks for the insight and some expert guidance. As a complete bearings novice, it's reassuring to hear from somebody who knows what they are talking about!

Sounds as if Nachi would be the preferred brand in your view – are you able to supply those or could you suggest where to obtain them?

Murray

[Ketan SwaliParticipant @ketanswali79440]

Hi Murray,

In our experience, for high end machine tools, Fafnir is technically the highest precision provider in Super Precision Match Pair, in line with Gamet (part of 600 Group).

In terms of marketing, RHP-NSK is the worlds most popular seller in Super Precision, as seen in the video link you attached earlier.

Then sit the most popular Japanese such as NACHI which go in high end Japanese machine tools with names I cant remember at present, followed by the rest, to include Chinese origin – sometimes dressed as German manufacture (which really p's me off)…The quality of the Chinese is fine, but to suggest it as German brand X is wrong.

Anyway, yes, Nachi is a preferred brand for us – technically and commercially – good balance. We can get it if you want it. Call us and speak with Ian or me.

Ketan at ARC.

[Ketan SwaliParticipant @ketanswali79440]

By the way, in our view/opinion, NACHI and RHP-NSK currently sit in the same quality bracket, with RHP-NSK dictating a higher price based on brand.

Ketan at ARC.

[Ketan SwaliParticipant @ketanswali79440]

Murray,

To the best of my knowledge, the Fafnir equivalent bearing number for the Super Precision Match Pair is:

2MM 207WI CR DUL where the 2 = 15 deg., MM = ABEC7 (ISO P4), DUL = Duplex, light preload

Even more better and more expensive then MM, they also do:

MMV = Super High Precision which sits between ABEC7 (ISO P4) and ABEC-9 (ISO P2)

or even higher:

MMX = Ultraprecision ABEC-9 (ISO P2)….very rare

Generally though, all of these Fafnir equivalents would be wasted on a Bridgeport…

Ketan at ARC.

[Allan Plant 1Participant @allanplant1]

Does anyone know how tight to do the bottom collet/ nut? the one with the grub screw, cheers

[Allan Plant 1Participant @allanplant1]

Thank you John

[Johnboy25Participant @johnboy25]

I would like to convey my thanks and appreciation to all who has contributed to this thread. This just indicates the power and usefullness of the forum in being able to tap into the weath of knowledge that's out there. The information has been of immensely helpful to me as I've been considering stripping my Bridgeport spindle down to replace the bearings along with some minor repairs to the quill feed mechanism. With the YouTube video clip it certainly enables you to see the problems hopefully before they might arise.

John

[KWILParticipant @kwil]

Allan,

The spindle nose piece is as tight as you can make it using a BOA rubber strap wrench, there is nothing to get hold of with which to measure a torque. How it was done in the factory I have no idea.It certainly does not run warm done that way but has no measure movement.

JS may well tell us how did it.

Edited By KWIL on 29/06/2017 19:06:21

[Matt C BeechParticipant @mattcbeech]

I've been looking at my spindle bearings and considering replacing them. I know its a sensitive job and good bearings are pricey. It's also pretty hard to learn enough about the bearings and find the proper specs for them to be able to find good prices (I'm in the UK). So I've written this doc to summarise all my findings and make it available to others who are looking at this.

https://docs.google.com/document/d/1B4wOqKddGJdzot_bYVlP38qmOxRBZChokvMLOQmkK0Q/edit?usp=sharing

Please let me know what I may have missed / not considered and so on. I realise there are large debates about clean rooms, cheaper bearing alternatives, but I have focused on equivalent specification replacements that can be achieved in the careful home shop.

[old martParticipant @oldmart]

Modern top brands like SKF, Timken and Toyo are so good that specially hand selected mega expensive bearings are hardly any better. I used a top Timken and bottom SKF ordinary grade bearings in the Tom Senior MT2 to R8 conversion and the spindle taper has 0.0001" tir or better which is plenty good enough for me, actually, I was delighted.

I have noticed complete spindles with bearings for Bridgeports available for under £200, does anybody know what they are like?

Edited By old mart on 28/08/2022 15:23:56

[HopperParticipant @hopper]

Looking at the prices of those matched pairs of bearings vs regular Timken, SKF etc single bearings I would need some convincing that they were worth 10 times as much. What difference does a "matched pair" make?

And how accurate do you want the spindle on a home hobby ancient old Bridgeport to be? If it is within one thou TIR it will work just fine. So what if the chip loading is one thou more on one side of the cutter than the other, if you are taking a 10 thou cut? Or even a two thou cut? Agonising over a tenth of a thou might be a bit of overkill. Your cutters, their collets and their holders will have more runout than that in most cases. But even regular bearings of good name brand should give accuracy somewhere down towards one tenth as Mart says above.

And regrinding the spindle after new bearings would also be overkill on a home hobby mill. Maybe appropriate for a super high precision grinder, not a flexible old Bilgeport mill. They are a good machine but not super hyper-precision.

Edited By Hopper on 29/08/2022 02:56:00

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