30,000 rpm high speed spindle bearing help

[rowow]

I am building a 30,000 rpm ATC spindle but I have a problem... The bearings... Searching for specs on a bearing is a pain in the ass and if it does provide specs the price is a bigger pain. There are "high speed" bearings listed on ebay with obviously no specs, even name brand ones (the Chinese bearings seem to be the only ones with specs). So does anyone know where I can search for 30,000 rpm bearings, i'm looking for 50 - 20mm ID bearings. I do not care about the OD/etc as long as the ID is within that range (since i'm building the spindle I can adjust a few measurements) and does "high speed" actually mean anything or is it just a marketing term that has no meaning.

Thanks!

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[ger21]

Part of the reason that spindles are so expensive is because of the cost of quality high speed bearings. The bearings in most quality spindles cost more than a complete chinese spindle.

I would think that at 30,000, you really want to be using ceramic bearings. And very expensive grease, to protect the expensive bearings.

[rowow]

I found relatively cheap ceramic bearing, but no specs. Would any ceramic bearings work? Again my issue is finding the specs for the bearings not what material to use.

[Jim Dawson]

Try this BNH007TU Nachi Angular Contact Spindle Bearing 35x62x14 ABEC 7

And this grease https://cnc-specialty-store.com/bear...FU1ufgodwd4C2Q

[rowow]

Great bearing but horrible price. I can buy a new spindle motor for the same price. Ill just get a cheap ceramic bearing instead.

[Jim Dawson]

Great bearing but horrible price. I can buy a new spindle motor for the same price. Ill just get a cheap ceramic bearing instead.

I guess it depends on how accurate and long lasting you want your spindle to be. As I recall, my BP clone spindle bearings were about $650 + about $250 labor at the local spindle shop. I thought it was a pretty good deal.

[underthetire]

That grease is great, but at 30K you may want to think about air/oil mist. Most machines over 10K rpm now use air/oil.

Sent from my SM-T813 using Tapatalk

[Jim Dawson]

That grease is great, but at 30K you may want to think about air/oil mist. Most machines over 10K rpm now use air/oil.

Sent from my SM-T813 using Tapatalk

You bring up an interesting point. Let's take the case of my router motor, a Porter Cable 7518, max rpm 21,000 rpm and it runs quite nicely for extended periods. Now the bearings are quite a bit smaller than what I would expect in a ATC spindle so the bearing surface speed is quite a bit less so maybe that is the key, smaller bearings.

The cheap import spindles also turn around 25K max and seem to last a reasonable amount of time, but maybe they have smaller bearings also, but the bearings have to be large enough to accommodate ER20 collets. I assume that these are grease lubricated.

I see ATC spindles in the $2.5K and up range. The bearings in those must be pretty good size, but the ones for routers have to be grease lubed, you couldn't have an oil drip.

Just some random thoughts I'll quit babbling now.

[ger21]

From my experience, most, if not all spindles used in Industrial ($100,000 +) routers use grease in their bearings. And these are all 18,000-24,000 rpm spindles.

We have a $400 tub of NBU15 at work, and I use it any time I replace bearings in a high rpm application.

[rowow]

Grease is used for 18,000 - 24,000 rpm spindles simply because thats a low speed. There are plenty of high grade steel bearing that can operate at those speeds under grease (as jim has linked). However speeds over 30,000 to 50,000 I have no clue how and what they use.

As for using smaller bearings, that is my goal hence the "50 - 20mm ID bearings" specification. I wanted to use 1 50mm bearing at the head, then multiple 20 or 30mm bearings further up depending on the cost difference.

Finally how do you seal the oil bearings? Do the bearings provide a seal on one side? Or would I need a separate seal system, if so what would I use for such speeds. I dont think a O right would be sufficient...

[ger21]

You need multiple bearings at the tool end. That's why almost all spindles use two angular contact bearings there.

[dharmic]

Dumb question - are you getting into the territory of air bearings here? Or are they incapable of dealing with the side loads on a higher power main spindle?

[rowow]

No question is a dumb question (except most questions) but the air bearings is very interesting, here is a video on them with a heavy side load


There are even spindles made of air bearings. So thank you so much for asking! ill start researching on them and how much they cost. Due to their simplicity I might even just make them.

[rowow]

These air bearings have gotten me really interested. Wikipedia states the only 3 disadvantages are 1: precision, 2: clean air, 3: requires power at all times
AKA the only problem is precision. The air bearings used in the video are graphite which is porous and provides a even air flow. Otherwise the more common system is this.
https://airbearings.s3.amazonaws.com...ng-example.jpg

And for linear bearing support

http://www.loadpoint-bearings.co.uk/...g-spindles.gif

I'm going out to my lathe right now and milling a miniature test piece. If I need to purchase a higher pressure pump I would much rather do that then spending $500 on bearings which will degrade quickly. So if this works out then thank you so much for the info!

My only question is why are air bearings not used more? Is it due to patents?

[Jim Dawson]

My only question is why are air bearings not used more? Is it due to patents?

It's due to cost and accuracy under high loads. Most of the cost is the precision required in the shaft and bearing blocks. Everything has to be pretty much perfect for them to work correctly.