6002RS Sealed Bearings / ie ball and roller type.....

[Tilt]

Anyone advise.............. A little info first.

I explained to the ebay seller (4Bearings) that I wanted it for a dremmel type grinder with 27000rpm and they said to purchase a branded one such as NTN, SFK or another such like, rather than the very cheap one.

I didn't get a reply when I asked about the clearance that was needed to be specified.

I purchased one off of them, an NTN 6002RS with C3 clearance. (all it says on the original one is 6002RS).

 

Anyway, I ask advice as the new bearing seems to be quite stiff for something that is supposed to be able to handle 27000rpm.

The original rear (but smaller) bearing in the grinder spins (by hand) really freely. beautiful and smooth too.

 

I have put (using a bolt through it) the new bearing in a cordless drill to see how it feels and whilst it is smooth, it drags quite a bit, . I also noted on google it mentions that most greased sealed bearings come from the manufacturers with too much grease in, which seems crazy.

 

I have asked a few questions but I think I am communicating with a sales person (via ebay messages) as they keep asking me what I am running it in, oil or grease.

They said it will run at 24000 rpm in grease and up to 27000 rpm in oil.

It's a sealed bearing and the grinder certainly doesn't have a reservoir for oil or grease, either, so what are they on about.

 

I am going to try and call the company tomorrow but not sure I will get to speak to a person that can explain properly.

 

I just want to know if the bearing is suitable as I suspect it is too tight.

 

Sensible advice gratefully received, if anyone knows about this stuff.

 

Cheers.

 

[J.R.]

A sealed bearing will always be stiff, a new bearing compared with an old worn one will equally feel stiff.

[moley]

Not sure the bearing description is correct, 6002 is a 15mm bore with 32mm O/D. I suspect your bearing is 6000 2RS, which is 10mm bore and 26mm O/D. 

A few tips on buying bearings. I avoid ebay on anything technical as there are a lot of 'fake' products packaged as genuine parts, unless the seller is a reputable business selling through ebay. I only buy SKF or FAG for standard metric deep grove bearings and I buy from Bearing boys, simply bearings or RS when I get a better price on quantities. I buy bearings from 5mm bore up to 80mm bore "RS or 2Z or sometimes no shields if it is in an oil filled gearbox.

If the original bearing was 2RS then it was fitted with plastic shields on both sides and these are normally used in a environment where dust and particles can enter the bearing and reduce it's life. The other shields are steel and will be listed as 2Z  or ZZ. The speed of the bearing varies depending on the shields. For the 6000 2RS SFK quote the reference speed at 67000 RPM and the limiting speed as 19,000 RPM, whereas the same bearing with steel shields 2Z the limiting speed is 34000 RPM, you will always feel more resistance with the 2RS shields, but if that originally fitted it should be OK. 

[Tilt]

@moley

It is a 6002RS........ it is in the front end of a Challenge Xtreme MSS6608 mini grinder. 

 

The bearing was purchased from 4bearings shop and they are an industrial bearings uk company. (The UK's largest bearing supplier according to them, anyway) Should be reputable though but yes, I get what you say about fakes. Very careful who I buy from too.

 

https://www.ebay.co.uk/itm/173758281890?var=472424954247

 

The other thing I note is that printed on the new NTN bearing seals it says 6002LU and on the box 6002LLUC3/5K (code T11907).

 

10 hours ago, moley said:

speed of the bearing varies depending on the shields. For the 6000 2RS SFK quote the reference speed at 67000 RPM and the limiting speed as 19,000 RPM, 

 

Do you know this info for the NTN 6002RS or where I might find it please???

 

And also, did I purchase the right 'bearing clearance' as this bit confused me a little. The choice was Normal-CN or C3........ I chose C3  as thought it may be better for high speed.

 

If you think it is the correct one and will be fine then I will fit it...........

 

Do you agree that them asking me 'what am I running it in, oil or grease', means that I am communicating with someone that doesn't have a clue what they are asking, or made a mistake, twice???

 

Really appreciate your time and help. Cheers.

[Tilt]

 

The new red bearing is just hung on the grinder bit for photo purposes.

Edited 23 July, 2021 by Tilt

[Tilt]

https://www.ntn-snr.com/sites/default/files/2017-03/en_ntn_ball_bearings_-_shield_and_seal_types.pdf

 

Looking through this for info............ I think the bearing they have sent LLU is not correct one for my application. It says it is 'contact type'.

 

States 'limiting speed' of 15/32/9mm LLU at 15000 rpm.

Edited 23 July, 2021 by Tilt

[moley]

1 hour ago, Tilt said:

https://www.ntn-snr.com/sites/default/files/2017-03/en_ntn_ball_bearings_-_shield_and_seal_types.pdf

 

Looking through this for info............ I think the bearing they have sent LLU is not correct one for my application. It says it is 'contact type'.

 

States 'limiting speed' of 15/32/9mm LLU at 15000 rpm.

I also found the same pdf file for the NTN bearings. I can't see what the difference is between LU and LLU and as you say 15000 rpm is the limiting speed. The equivalent bearing from SKF is the 6002 2RS, which has a reference speed of 50000 rpm and a  limiting speed of 14000 rpm. The SKF 2Z steel shielded bearing has a limiting speed of 26000 rpm, but will be prone to failure when the grinding dust gets past the shield. I use INA bearings for some special applications and their sealed bearing has a limiting speed of 13100, so all the bearing manufacturers appear to have similar limiting speeds way below 27000 rpm 

C3 is a closer tolerance on the size of the bore.

Quote

The limiting speed indicated in the product tables is a maximum speed valid for the standard bearing execution that should not be exceeded unless the bearing design and the application is adapted to a higher speed. The limiting speed can only be exploited, if the bearing is properly lubricated

 Clearly the manufacturer has gone for the sealed bearing to prevent the ingress of grinding dust. I assume you are replacing the bearing because it has failed, in which case the reason for the failure could be caused by the motor speed being too high for the specification of the bearing. 

I think you have the correct bearing and it will 'free up' after 'X' amount of cycles, but as it is running 80% faster than it was designed to run at I guess it will fail sooner than it should.

Sorry, but I don't know what else to suggest to resolve the problem.

[J.R.]

What is the reference speed and more importantly where does this get used in bearing selection?

 

I understand the limiting speed but its odd to have a reference speed 3 times higher.

 

I used to design special purpose machinery with roller bearings amongst others, clearly I have forgotten more than I ever learned, - use it or lose it!!!

 

The bearings on my Maytag commercial washing machine (that have to be changed quite frequently) are exactly the same as the crown wheel bearings on the diff casing of my Lotus Elan!!!!

[Tilt]

Thanks @moley

The LU is just a single seal vs the LLU being sealed both sides. (see info at bottom of ....... 1. Bearing Design and Features

 

I guess for me now, either fit it and hope it is fine as it doesn't get loads of use anyway, or........

Try a ZZ/2Z shielded bearing as it still states as 'good' for dust proofing.

 

I may purchase a ZZ type as these bearings at this size are surprisingly cheap anyway.

 

Thanks for your help and advice. 

[moley]

15 hours ago, Tilt said:

Thanks @moley

The LU is just a single seal vs the LLU being sealed both sides. (see info at bottom of ....... 1. Bearing Design and Features

 

I guess for me now, either fit it and hope it is fine as it doesn't get loads of use anyway, or........

Try a ZZ/2Z shielded bearing as it still states as 'good' for dust proofing.

 

I may purchase a ZZ type as these bearings at this size are surprisingly cheap anyway.

 

Thanks for your help and advice. 

I can see that LU is single sided and LLU is both sides sealed, what I couldn't see in the information was a speed limiting rpm for for the LU bearing.

A simple solution could be to prise the seal out of one side of the bearing and convert it to an LU version, then you still have a sealed face externally to prevent the ingress of dust.

[Tilt]

I fitted the one supplied but it gets very hot close to the bearing (carefully feeling the tightening nut / sleeve for heat) in a very short time so I will use it short term for no more than a minute or two at a time. At least I can use it.

 

I'm guessing an LU version (including adapting an LLU) would lose it's grease wouldn't it???

 

Well, will get one or the other of ZZ or Non Contact type 2RS LLB ............. either should prove to be better suited.

 

Cheers guys.