# Spindle bearings



## NGillem (Mar 9, 2017)

Hi guys,
I have a small Harvey butterfly sg 48 surface grinder.  I'm afraid I'm in need of new spindle bearings and before I dive too deep in it I wanted to test the waters and see what information was out there regarding which bearings may be needed.  I know these are a close copy of the Sanfords with the same part number.  I do not have any oil cups so I'm assuming they are some type of sealed angular contact bearing I have nothing invested in the machine but would like to see what I can do with it.  Thanks for any and all help!


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## Bob Korves (Mar 9, 2017)

Rebuilding surface grinder spindles is really something that should be done by professionals who have clean rooms, vibration analyzers, and other tools of the trade.  The spindle needs to be smooth running, have no play, and be accurate to high tolerances for the grinder to do it's best work.  $$$$$  That said, I recently rebuilt the spindle on my 1946 B&S 2L grinder in my shop.  The previous two master machinists who tried to rebuild it failed.  My spindle is a plain bearing spindle, running super light spindle oil with 110 millionths clearance between spindle and bronze bearing boxes.  Anyway, I was able to fake the clean room, obtained the special oil (ISO 2!), put on my best professional face -8^), got it working, and it is working fine now.  It took quite a few fussy hours of planning and work.  I think the Sanfords are all small grinders, perhaps yours is 4x8" by the model number.  If you want to tear into it, go ahead, but this is not replacing the wheel bearings on your car.  Everything needs to be done right, done carefully, the bearings must be carefully fitted, and everything must be CLEAN(!) as it goes back together very carefully.  Did you notice the multiple use of "carefully"?  If you take your time, do it right, and approach it with the correct mindset, you will probably have success.  The other issue is the price of the bearings.  For many surface grinders, the bearings are jaw dropping expensive.  Maybe not so much for your Sanford, I really have no idea.  If it is running OK, I would leave it alone.  If it is failing or failed, well, it is already broken, you can't make it worse than that...  Keep us informed of what you do and how it goes.  Everybody likes a challenge, and especially something that many say is impossible to do in the home shop.


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## Bob Korves (Mar 9, 2017)

I just did a bit of a web search and found that the spindle on the SG48 is driven by a belt from the motor.  Make sure that whatever problems you have are in the spindle itself, not the motor or the belt.  Take the belt off and turn the spindle by hand and see what you have -- if you haven't already...  On a machine that old, it might just be dried up grease in the bearings.  If you have it narrowed down to the spindle, take it apart and see what you have in there.


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## NGillem (Mar 9, 2017)

Thank you for your responses and help..... yes the machine does run but it was in fact the loss of the belt that got me looking at the spindle.  I have done a fair bit of research and understand the concerns of spindle repair in a less then an adequate environment.  Maybe it is just old grease but to my hand I feel flat spots on the races.  I just wanted to gather as much info as I can because at some point or another I will disassemble the machine.  I know the machine doesn't hold much value and it was given to me so anything I can do I will try!  Thanks!


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## Bob Korves (Mar 9, 2017)

I also looked to see if anyone posted the bearing numbers, but no joy...


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## Holescreek (Mar 9, 2017)

Best thing to do is take it apart and write down  the numbers they used then call your local bearing distributor to see if they are available and if there are upgrades available.   New bearings for my K.O. Lee were pretty cheap going that route.


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## Kernbigo (Mar 10, 2017)

i used to rebuild high speed spindles and it may be possible to save the bearings by cleaning them and repacking with high speed spindle grease( only pack 1/3 capacity )


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## NGillem (Mar 12, 2017)

Hi guys again thanks for all of your comments and suggestions.  I had a little time this weekend and stripped down the spindle upon my inspection I found mostly old dried grease,  I cleaned everything up to get a closer look and visually I see nothing obviously wrong so I'm going do a better cleaning in the ultrasonic cleaner and get ready for reassembly my question is grease.... Is my best option the kluber stuff I have found countless references on or will any high speed spindle grease be sufficient.  I know this may not be the best approach but spindle disassembly is easy enough I dont mind giving it a try.  Im sure a microscope would reveal many more imperfections but I can live with that. 
Thanks


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## Holescreek (Mar 12, 2017)

Speaking only for myself, If I found as you described "I found mostly old dried grease" and "but to my hand I feel flat spots on the races." I wouldn't waste my time adding grease. Lipstick on a pig.


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## Bob Korves (Mar 12, 2017)

Did you get the bearing numbers?


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## NGillem (Mar 12, 2017)

I did not get any bearing numbers they must be stamped on the outer race which is pressed in the tube and I did not yet remove them.... my time was at that point limited I'm hoping to get back to it this week


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## Kernbigo (Mar 12, 2017)

in your case i would repack the bearing 1/3 capacity with any high speed spindle grease you have. I used mobile plex 46 i believe when i rebuilt high speed spindles oil is 3 time better if you can rig up a oil mister


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## Tinmuk (Apr 2, 2017)

Can you measure the ID, OD and width of the bearings. I can cross refence the bearings for you if you cant find the numbers.
A lot of the older light duty grinding spindles used duplexed bearings instead of angular contact bearings. Some of the early Du-More spindles just used preloaded standard bearings. Angular contact bearings are usually used when there is significant thrust load


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## fitterman1 (Apr 2, 2017)

Check your shells for Brinelling if you think you feel flatspots. This will definitely make you change your bearings.


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## rowbare (Apr 3, 2017)

The Sanfords used magneto bearings. The older ones used E-14 size the newer ones used E-15. They aren't the easiest to find but there are a few US vendors who have them on eBay and if you google E-14 you will find some UK sellers who have them. They aren't horribly expensive. 

http://www.d-and-d.com/misc/MANUALS/Sanford/SCANNINGS/Manual.pdf

bob


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## NGillem (Apr 3, 2017)

Thanks guys for your continued help!  I have everything thoroughly cleaned but have not found the time to get back to it my google search on the previous bearings numbers posted look to be very promising.  I will have to do some measuring to confirm which ones I may need,  I may try to reassemble just to see what happens to the naked I'm having a hard time finding any defects.  There are no visible bearing numbers on the races and the outter race is positioned in such a way that the means of removal looks too be possibly running a weld bead inside of the outter races in hopes of shrinking it.  Because previously I had no bearing numbers I've been reluctant to further ruin what I already have.
Thanks, Nate


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## Tinmuk (Apr 3, 2017)

Nate,
Roughly how big are the bearing? If they are around 1.5 "OD or smaller, I can probably help you. I have a warehouse full of bearings in stock. Most are miniature instrument bearings.


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## Tinmuk (Apr 3, 2017)

BTW, can you post a pic of the spindle?


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## NGillem (Apr 3, 2017)

Tinmuk, I will snap some pictures and get the dimension tomorrow evening when I'm around the machine.  From the bearings numbers posted earlier and using my memory I would say the Od is under an 1.5"
Thanks


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## fitterman1 (Apr 4, 2017)

Before running a weld bead and destroying that race, can you warm up the housing?
If the housing is aluminium/cast iron it will expand at a greater rate than the steel brg race and may drop out with some persuasion.


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## markba633csi (Apr 4, 2017)

What's a magneto bearing? What's a magneto? Just kidding I know what a magneto is.
Mark S.


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## NGillem (Apr 4, 2017)

Here are some pics the bearing bores measure
1.853 and the shaft journals measure .787 and the inner race measures .575 wide....


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## Tinmuk (Apr 4, 2017)

You have a 6204ZZ bearing with phenolic cage. Ill look thru my stock tomorrow and see if i have any. Do the end caps press againgst the inner or outer race?
Is the any room behind the race that is stuck in the housing?
Where are you located? I may be able to remove the old races and install the new ones for you.


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## fitterman1 (Apr 4, 2017)

I reckon they are L20 bearings, 6204's are normal deep groove ball brgs, they dont dismantle like magneto or angular contacts. Being deep groove there is no adjustment to minimise clearances which means any tightening of the spindle nut will force the inner races towards each other with catastrophic results. Any machine spindle of such precision will have angular contact bearings and is adjusted accordingly.

My FAG bearing book lists a B7204E.T.P4S.UL as the correct brg to use, good for 30000 rpm with grease or 45000 with oil. Dimensions are 20 x 47 x 15mm in metric.

SKF list a 7204BECBP in their book. SKF rate theirs at 18000 rpm but don't mention lubrication.
The only difference is the SKF brg is 14mm max width while the FAG goes to 15mm.

I had a good look at your pictures and noticed how there is a step behind the innermost brg races. I had a similar situation on my G0602 headstock and not having the correct puller to extract them I ground out two opposing recesses in the casting to get some purchase with a pin punch. After the shells were out I filed them larger and dressed them for future access. You may be able to do the same. I think your shells are not fitted with much of an interference, more a nice hand press fit if anything.
Good Luck.


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## NGillem (Apr 4, 2017)

There is a spacer that pushes against the inner race on the right hand side off the top pic... the other larger pieces are end caps that keep out debris from what I can tell.  There is no room to get behind them, in the second pic you can see shims behind the race I'm assuming to set bearing preload those shims can be rotated but no other movement to speak of So no real room to get behind.
Thanks again for all the help


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## Bob Korves (Apr 5, 2017)

Those are not 6204ZZ bearings...


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## fitterman1 (Apr 5, 2017)

NG, that's correct, those shims are for setting preload, same for any other machine spindle. Considering the bearings you removed are either magneto or angular contacts, thats all I would be searching for to replace the originals with.
I wouldn't want you to destroy your grinder because someone recommends changing them to another format. I like the fact you're not scared to take on a job like this because in reality it is simple, its the bearing adjustments that cause the most grief.
cheers


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## fitterman1 (Apr 5, 2017)

NG, I noticed in your last post that you said "the shims can be rotated". That seems to tell me that there was excess clearance in the assembly, or that particular shell has moved somehow. Indicating that there is a minimum amount of interference holding the shell in. Maybe your ultrasonic cleaner started walking it out.


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## Tinmuk (Apr 5, 2017)

For purely radial loads such as a surface grinder, _properly pre-loaded_ deep groove bearings will work just as well as angular contact bearings at a much lower cost. For hobby level the cost difference can mean a lot. For a mill spindle angular contact duplexed bearing are a requirement, due to the thrust loading.

Nate can decide which route he wants to go. I am suggesting an affordable solution.  Worst case, he can replace them later with  the more expensive angular contact bearings.

Nate, keep in mind whichever bearings you decide on, the shims will have to be adjusted for proper pre-load.  Adjusting the pre-load to run properly at operating temperature can be difficult to set. If you don't have enough clearance when cold the bearings may seize at temp.


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## Tinmuk (Apr 5, 2017)

I have some 6204 in stock if want some to play with. They will need to relubed with high speed grease or oil. PM me if you want them, no charge.


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## Bob Korves (Apr 5, 2017)

Surface grinders do not have purely radial loading, mostly perhaps, but not all.  Ever heard of side wheeling?  In addition, when you use radial bearings with side loading, even if only for the end thrust to axially locate and support the spindle and grinding wheel and resist deflection of the grinding wheel, the bearings will not be in their best loading orientation against the races and will fail early.  Radial bearings should not be end loaded, and the grinder spindle preload does exactly that.


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## NGillem (Apr 5, 2017)

Thank you tinmuk that's an very generous offer I want to replace them with what ever will give me the best possible results. with zero invested in the machine I don't mind spending some money although if the alternative to your suggestion is going to be $400 a piece in bearings well the machine probably isn't worth it.... as far as setting preload is that measured axially for example if there .010 movement with no shims I proceed to add ..10 plus some for preload or do you take a rotational measurement with a low reading torque wrench like you would for setting up pinion bearings in a differential for car/truck? Again thanks to all for the help and suggestions!   In the mean time I will see if I can remove the outter races for which ever direction I go


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## NGillem (Apr 5, 2017)

I got it out....


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## fitterman1 (Apr 5, 2017)

So now you have numbers. I see Fafnir but can't see numbers, what are they? And how did it come out?


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## NGillem (Apr 5, 2017)

The numbers are 204WI.... I used my fingers and reached in there it didn't feel like it moved but the shims loosened up so I got a soft punch and tapped against the shim very light and worked out it really came out easily


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## Tinmuk (Apr 5, 2017)

Nate,
That is the basics of setting axial preload, the last little bit of how much to add after the play is gone is critical. You may want to just take out the play and see how well it grinds after operating temp is reached. If it performs well then just leave it.

Bob,
You obivously understand bearings well. However all bearing sets should be preloaded to increase life and axial stiffness, including deep groove radial bearings. 

Angular contact bearings have a slightly higher shoulder on the thrust side,  to allow the balls to ride up higer during preload, typicall 15 degrees instead of about 10 degrees. Other than that they are made identically. 

I have designed angular contact versions of deep groove bearings where our customer needed more thrust load and the raceway curvature, number of balls, retainer did not change.


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## fitterman1 (Apr 5, 2017)

Its now called a 7204WN . I thought they weren't in there that tight See page 218, 4th bearing number down.
Timken will stock them.


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## fitterman1 (Apr 5, 2017)

Suss out this link

http://www.ebay.com/itm/New-Fafnir-...163425?hash=item2ca2662221:g:cjIAAOSwKIpWCXBI


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## NGillem (Apr 5, 2017)

Wow that's great thanks for your help I'm going to order a pair! Just out of curiosity where did you get that part number I checked out the link and could not find that number referenced on the page


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## fitterman1 (Apr 5, 2017)

In the header, its the same brg, even the dimensions are displayed.

*New Fafnir Angular Contact Ball Bearing, 20mm Bore, 47mm OD, 14mm Width, 7204W*

*Did you just buy them, there was 3 left an hour ago?*


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## NGillem (Apr 5, 2017)

Oh yea I bought them.... I was talking about the fafnir PDF


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## fitterman1 (Apr 5, 2017)

Download the pdf and then open it and go to page 218. I mistakenly saw page 48 of that particular section. Go to page 218 and then you'll find the bearing, you'll also note my mistake. Apologies, I'll change my earlier post


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## fitterman1 (Apr 5, 2017)

Download the pdf and then open it and go to page 218. I mistakenly saw page 48 of that particular section. Go to page 218 and then you'll find the bearing, you'll also note my mistake. Apologies, I'll change my earlier post.

I've made a double post, how do you delete these?


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## NGillem (Apr 5, 2017)

No need to appologize.... looking around through there I did find the exact number of the bearing I removed it is on page 56 of the pdf I'm wondering the difference maybe the abec rating


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## fitterman1 (Apr 5, 2017)

That one would do the trick considering its the same number. It has a lighter thrust rating than the 7204W, you can tell by the angles of contact.
The 204WI looks like a 20 degree contact angle, meaning its capable of higher speeds with light thrust capabilities.
The 7204W has a 40 degree contact angle so it is capable of absorbing greater axial thrust or has greater precision in maintaining axial position of the spinning shaft.
I think the 7204W has more precision and is no doubt good for 20000 rpm. What spindle speeds is your machine rated at?


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## NGillem (Apr 6, 2017)

Thats a good question but I would have to say well with in that range! Thanks


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## Bob Korves (Apr 6, 2017)

The 204WI bearings are the high precision ABEC9 type, and they have a different contact angles.  With a quick and not exhaustive search, I did not see any of the 204WI bearings for sale other than at retail.  They will be very high priced, my guess is at least $100 each, maybe more, maybe MUCH more unless you get lucky.  The ones you ordered, 7204W, will do the job.  The shim stack needed may be different with those lower precision bearings due to different tolerances, but the shim stack must be chosen for the desired preload anyway.  The other dimensions are also tighter on the 204WI bearings, and so they probably run somewhat smoother, but they will be a lot better than what I could see in the races of the ones you removed from the machine, and you probably would not know the difference unless somebody told you or showed you with a sensitive vibration tester.  The price is right and they will work.  I suggest you give them a try.


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## fitterman1 (Apr 6, 2017)

For example a 100mm pulley on a motor doing 3000 rpm will give you a spindle speed of 5000 rpm if the spindle pulley is 60mm diameter


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## Bob Korves (Apr 6, 2017)

My surface grinder uses 7" wheels and has a spindle speed of 3200 rpm, and the wheels are rated to 3600 rpm.  That small grinder may use smaller wheels, and that would likely increase the spindle rpm, but probably not over about 5000 rpm at most.


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## fitterman1 (Apr 6, 2017)

That's a very relevant point to bring up Bob. NG needs to calculate his final spindle speed so he can select suitable wheels to use.
So he needs to ckeck the speed rating on his motor nameplate + measure his driver pulley and driven pulley.
But we're getting ahead of ourselves here, and need to focus on getting his spindle back together.


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## Bob Korves (Apr 6, 2017)

What he really needs is a factory manual for the machine (assuming he doesn't have one), stops all the guessing...  When in doubt, RTFM!


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