Any bearing experts aboard?

[slow-poke]

I'm looking for a matched pair of angular contact bearings. Typical deep groove bearings in this size have about 0.002" of play laterally even when snugged up and the same applies to angular contact bearings if you don't order them as a matched set, the matched sets are precision ground so that when preloaded, the outer and inner rings have the same width resulting in near zero end play. Matched sets can be very expensive.

I was able to find a pair of matched NSK's and they allowed me to get the total error on the X axis of my mill down to 0.0003", and I'm happy with that goal was < 0.001"

Now I need another set for another axis and found these old stock on ebay. They appear to be a matched set (same box), but I'm not sure they might just be two unmatched. I asked the seller and he has no clue. I tried to find details online but no luck.

Does anyone have any insight?

Fafnir 2MM9101WI DUL Precision Angular Contact Bearing 12x28x8mm BOX OF 2 | eBay

Find many great new & used options and get the best deals for Fafnir 2MM9101WI DUL Precision Angular Contact Bearing 12x28x8mm BOX OF 2 at the best online prices at eBay! Free shipping for many products!

www.ebay.ca

 

[DavidR8]

Have you contacted Bearings Canada?

 

[slow-poke]

For a quote or info on this particular set?

Quotes are typically in the many hundreds of dollars for a pair and that is beyond my budget.

For example: https://www.bearingscanada.com/7001CYDUP4-Nachi-Angular-Contact-12x28x8-Abec-7-p/kit10868.htm

 

[DavidR8]

Yup, pre-Covid I put Naachi bearings in my RF-30 clone and they were about $200 for a pair from Bearings Canada. So definitely not cheap

 

[Maker Mike]

Do the bearings have the v on them to indicate how to align them? Are you worried that you are a buying a set of matched bearings that aren't actually matched, or the box just originally had two bearings in it that were never intended to be a matched set? I'm no bearing expert.

 

[slow-poke]

Do the bearings have the v on them to indicate how to align them? Are you worried that you are a buying a set of matched bearings that aren't actually matched, or the box just originally had two bearings in it that were never intended to be a matched set? I'm no bearing expert.

Most likely the set in the eBay listing are a matched set, but the seller isn't sure and I don't want to spend $100 to get an unmatched (useless to me) set. I found another set that are definitely matched for US$65 with free shipping and they are on the way. The listing above from Bearings Canada is $450 before tax and shipping , seems a bit over the top for a couple of small P4 bearings. I can swallow $100 to get under 0.001", but more than that just seems excessive.

 

[Proxule]

Do the bearings have the v on them to indicate how to align them? Are you worried that you are a buying a set of matched bearings that aren't actually matched, or the box just originally had two bearings in it that were never intended to be a matched set? I'm no bearing expert.

Also called duplex bearings, and often are very pricey, More then our resident fast-poke is willing to spend I think.

 

[Proxule]

@slow-poke are you referring to true AC cartridge bearings or a cup and cone style?
I suppose ebay is the best bet but who knows if they are matched, Aliexpress? lol

 

[slow-poke]

I ordered these: https://www.ebay.ca/itm/385567495647

If I were foolish enough to pay the $1k local price, tax alone would be more than what I paid for the previous set that are already on my machine, picked up that set for $50 offer that was accepted.

https://www.motioncanada.ca/products/sku/00113171?fromSisterSite=true

When I set out on this project I was aiming for <0.001" using inexpensive parts. From what I have read the better quality CNC machines are accurate to 0.0002".

Sub 0.001" is easily achievable with fairly inexpensive parts if you close the feedback loop with linear scales. With eBay $100 ballscrews and $100 bearings I'm consistently getting < 0.0004" Hopefully this will not grow over time, time will tell.

Price of everything goes up exponentially when aiming for those 2/10s type machines, ground ballscrews, super duper bearings etc. all well beyond my hobby aspirations.

I just want to be able to machine a relatively round hole with enough accuracy to hold a press fit bearing without the need for a rotary table and that's not so easy to do open loop even with backlash compensation.

 

[Mcgyver]

What you get with matched pairs is the right preload ground in. P4 AC's "universally matched" should be <100. That's the only difference. You can achieve the same thing with universals and grinding spacers (done it a few times)

Bearings are really really good nowadays. The big brands have got them dialed in to perfection and their manufacture is highly automated. Great news for us because most of them are excellent, at least from a recognized brand. And cheap (unless you want matched).

I have had this from first hand conversations with engineers at two of the major bearing companies: The higher cost of the P4's (and presumable P2's) is the time it takes to check and certify them. They all come out of the same pile of produced bearings. Now, there is a chance the one that is grabbed and inspected for P4 status gets rejected, but these engineers advised that doesn't happen much because production is so automated and dialed in.

Finally, you can expect a similar level of very small variation with the preload of "universal" P4 AC's. Non-matched, called universally matched, do still have a preload. You don't have to precision grind spacers, you can just assemble the universals and they will be very very good, maybe as good as matched. You can't guarantee they'll be as good and you can't specify or control the preload like you can with matched, but they will be awfully bloody good.

They sort of prey on the end user; the OEM price on those expensive bearings are 1/4-1/3 of what you see listed. At that level it becomes somewhat more reasonable to choose matched sets for convenience and certainty of the fit.

The matched are so expensive because each race is ground individually, so its very labour intensive vs the production line. Because of this, the waits for uncommon size can be astounding. I'm 18 months waiting on a less common low profile size from SKF. When ordered them in dec 2022 we were told Italy has that size set to run mid 2024.

 

[Jswain]

Any transmission/bearing supply stores in your area? We used TSL in calgary at my last job, and I was amazed at their supply/knowledge of bearings/seals etc. Seemed like they could get just about anything.

Walk in with a totally random bearing/seal off a piece of equipment and they had several options in stock

 

[Tom O]

I’ve always gone there

 

[slow-poke]

Joe, local bearing place quoted $600

Mcgyver, your post makes a lot of sense, I was thinking about modern manufacturing processes from quality companies (Germany, Japan, USA, others) and was trying to make sense of how can they produce bearings with a bunch of tight tolerances and then have one tolerance that you need to pay hundreds extra for, doesn't make a lot of sense. Now if the bearings are manufactured in a iffy quality country all bets are off, case in point I just tried a pair of unmatched 7001 angular contact bearings China-Amazon special (dirt cheap so I just had to try, how bad could they be?) BAD, really really bad! as in complete junk. 0.02" of end play, perhaps good for roller skates.

The first set of eBay NOS NSK's are perfect (old style blue box), I hope the set on order are the same quality (new gold box), apparently there are now NSK clones and NSK has gone to the trouble of including a unique QR code with each bearing that can be scanned with a tool on their website to verify it's genuine. If what I receive is a clone I'm getting a refund. Fingers crossed.