[Jason M]

Interesting because I was under the impression that ball screw support bearings where a whole different series enhanced to handle thrust loads. At least the bearings I've seen marketed as ball screw supports where designed with a different contact angle and hefty races.

Depends on what you mean by "different series" of course but I think I know what you mean (referring to 7XXX series?) and if so you're right on both counts. The term "angular contact" carries heavy connotations of the 7XXX series but it's used as a design term more than for one particular series (by me at least), in general meaning "not purely thrust or radial". Most common in the 7XXX series of angular contacts are 40 degree contact angles (72/73XX series) with 15 and 25 degrees in the super precision (more commonly light/ultra-light 7XXX(X)) but you'll find angular contacts in other series from 8 to 45 degrees that I'm familiar with, the range may in fact be wider.

We were not talking about self-aligning Bearings, but when you put the 5300 number in there, these come in that series

I wasn't aware of that, never run across it, what manufacturer uses 5XXX for self-aligning ball bearings? Every manufacturer I'm familiar with uses the 53XX and 52XX series numbering for double row angular contact ball bearings. I don't have a lot of experience with self-aligning ball bearings but I thought I recalled the SKF nomenclature being 1XXX and 2XXX

Apologies to the original poster for the tangent

[mactec54]

Depends on what you mean by "different series" of course but I think I know what you mean (referring to 7XXX series?) and if so you're right on both counts. The term "angular contact" carries heavy connotations of the 7XXX series but it's used as a design term more than for one particular series (by me at least), in general meaning "not purely thrust or radial". Most common in the 7XXX series of angular contacts are 40 degree contact angles (72/73XX series) with 15 and 25 degrees in the super precision (more commonly light/ultra-light 7XXX(X)) but you'll find angular contacts in other series from 8 to 45 degrees that I'm familiar with, the range may in fact be wider.

The Bearings Wizard is talking about, are not regular/standard Bearings off the shelf heavy duty A/C Bearings, they are mostly custom made to each manufactures needs they don't have a series number, they have there own part numbers for the Bearings, & in most cases can only be brought from the machine builder

[wizard]

Actuall Barden now catalogs standard of the shelf ball screw support bearings. Honestly it has been so long I'm not sure these are what we where ordering way back then. I actually think we where using standard angular contact bearings. It has been a very long time since I was working on CNC lathes daily.

The Bearings Wizard is talking about, are not regular/standard Bearings off the shelf heavy duty A/C Bearings, they are mostly custom made to each manufactures needs they don't have a series number, they have there own part numbers for the Bearings, & in most cases can only be brought from the machine builder

We use to run into those builder only bearings too. Not good for the pocket book that is for sure.

[arvidj]

...

If you have (1) of this type of bearing on each end of the Ballscrew, they will do a great job & just as good as, 2 expensive precision Bearings on (1) end Which you have to seal

Good brand name Bearings like this have around .0002 clearance, Like SKF Etc, so with (2) one on each end, you can put the Ballscrew in tension/light preload, to take up any clearance, so you get the best of both worlds, Great support & low cost.

...

I have been following this very interesting thread and admit that I do not have anywhere near the experience or expertise of those participating. However, I do have a question related to the "so with (2) one on each end".

There seem to be recommendations that the ballscrew support be fixed at one end and floating at the other to address thermal expansion issues. "so with (2) one on each end" makes perfect sense to address what ever small amount of clearance the bearings might have but also seems to go against the "one end fixed, one end floating" recommendation.

As a neophyte I guess I need some help getting my head around this.

Thanks,
Arvid

[mactec54]

arvidj

Good question

It is your choice of how you want to arrange your bearings,You don't have to have (2) A/c Bearings, one end can be floating if you want, just (1) fixed end


Having (2) A/C Bearings of this type, you can tension the ballscrew, which has many benefits, most machining centers, the ballscrews are in tension, just as I have said, in a much bigger scale than this, it does not need much to do a preload like this, 4lbs to 8lbs is all that is needed, depending on the ballscrew size, & Bearing size

thermal expansion issues. not a problem at this level of machine building

This is a standard for Ballscrew Bearing mounting

[arvidj]

Thanks for the clarification.

If I understand the thread, the recommendation for ballscrew support bearings for a cost effective yet accurate DIY CNC conversion is to use 5200 series bearings in tension.

Can we assume this recommendation applies to tables as large as 1000mm and 25x5 ballscrews (what seems to be the largest table and most common ballscrew used in the CNC conversions of the "Super RF45" mills offered by IH, Machine Tools Warehouse, PM, etc.

Please correct me if I have interpreted the thread incorrectly.

Arvid

[Jason M]

If I understand the thread, the recommendation for ballscrew support bearings for a cost effective yet accurate DIY CNC conversion is to use 5200 series bearings in tension.

That is what I hear mactech54 is saying. The only figure given in regards to accuracy however was .0002 clearance in the 5200 series - no indication of whether that's inch or metric or what size of bearing. Since it to the tenth you can assume inch and I don't think in context it could be metric. So he's saying 5 microns internal clearance for the 5200 series of bearings which is not correct, see below.

Can we assume this recommendation applies to tables as large as 1000mm and 25x5 ballscrews (what seems to be the largest table and most common ballscrew used in the CNC conversions of the "Super RF45" mills offered by IH, Machine Tools Warehouse, PM, etc.

The larger the bearing in the series (5200) the larger the spec for internal clearance, see attached from an SKF catalog

Attachment 197308

The big half of "cost effective" is "effective". Make sure you can live with what you're getting before you get it!

[mactec54]

Jason M

You are talking like a salesman, you are not an engineer so should not try to give ( Negative ) information, which you seem to be trying to confused everyone with

Angular contact Bearings of any type have Zero Clearance when installed correctly

Please Post tell everyone why these Bearings 5200/5300 Etc have a Listed Clearance????

Arvidj many of the kits for the RF45 mill are using this 5300 type bearing on there ballscrews, you should ask some of the kit users how there bearings are working for them, There are also some that are using (2) A/C Bearings on the Fixed end

It is as I have said in other posts, it is up to you, as to how much money you want to spend for your Bearings, when someone puts C7 grade ballscrews on a machine, these Bearings are way better than what is needed to do the job

If you are using C1 to C5 Ballscrews then you need to use Bearings of the same quality/ precision

[109jb]

my bad. sorry

[Jason M]

You are talking like a salesman, you are not an engineer so should not try to give ( Negative ) information, which you seem to be trying to confused everyone with

You are correct, my only experience with double row angular contact bearings was to move them in and out of inventory 20 years ago. I am not purposefully doing anything negative or confusing. I am not your adversary, I am asking questions to clarify things, your statements, that I do not understand.

Angular contact Bearings of any type have Zero Clearance when installed correctly

Please Post tell everyone why these Bearings 5200/5300 Etc have a Listed Clearance????

You say "when installed correctly" - that's the main thnig I'm not understanding, how to install correctly and achieve the zero clearance. I assume the clearance is taken out via compensating shaft and housing fit? What are those fits and are they easy/cheap enough to achieve, keeping the cost of this double row alternative down?

I find your assertation that this can be done to be really interesting, it's a huge cost difference that I'm sure a lot of people could take advantage of. I would like to understand the hows of it

[packrat]

@Jason and mactec, you guys are talking about two completely different double row angular contact(DRAC) bearings!

Jason, the 5200/5300 do have an axial clearance. It can't be eliminated, because of the way they're made. Two sets of balls in a one piece outer and one one piece inner rings.

mactec, the bearing you showed in post #20 is a special DRAC bearing. It is zero clearance. Two rows of balls in a one piece outer ring with a two piece inner ring. Zero clearance or can be pre-loaded. This type is also called "four point contact" by some makers.

And not all AC bearings are zero clearance, only the ones made for "duplex" installation. Though the ones not made for duplex can be used, if you shim them between the rings, to make them zero clearance or pre-loaded.

See this link by SKF - Double row angular contact ball bearings - SKF.com/Products

[mactec54]

[QUOTE=packrat;1334654]@Jason and mactec, you guys are talking about two completely different double row angular contact(DRAC) bearings!

No we are not, I'm just showing the different options

[QUOTE]Jason, the 5200/5300 do have an axial clearance. It can't be eliminated, because of the way they're made. Two sets of balls in a one piece outer and one one piece inner rings.

This is not correct the clearance can be adjusted, if fitted correctly, they will have Zero clearance in the bearing when fitted

[QUOTE=packrat;1334654]mactec, the bearing you showed in post #20 is a special DRAC bearing. It is zero clearance. Two rows of balls in a one piece outer ring with a two piece inner ring. Zero clearance or can be pre-loaded. This type is also called "four point contact" by some makers.

Nothing special about them, I make them, they are just another Bearing style

[QUOTE=packrat;1334654]@And not all AC bearings are zero clearance, only the ones made for "duplex" installation. Though the ones not made for duplex can be used, if you shim them between the rings, to make them zero clearance or pre-loaded.

Not correct, when A/C bearing are assembled correctly, they will have zero clearance, no matter what type, If they do not then the Bearing will have a short life

[mactec54]

Jason M

You are on the right track, to adjust the clearance in these bearings, I found it is always better to work with the shaft size to adjust the clearance, in any bearing, not just this type, It take's very little, sometimes it is just a normal bearing fit from what the manufactures recommend, some times a little more is needed to get the zero clearance, it just depends on the quality of the Bearing you start out with, & how much clearance it has

The question I asked, was, why these Bearings 5200/5300 Etc have a Listed Clearance????

The only reason they have a clearance is so they can be assembled, I have had some with as little as .005mm clearance (MRC brand owned by SKF)

The most clearance I have ever found with this type of bearing is 0.022mm, the bearings I use have before assembly have 0.01mm on average & less, with this small amount, it's easy to adjust the shaft size to give you the zero clearance, this is almost a normal manufactures recommended shaft size, so to get a zero clearance does not take much at all

[packrat]

[QUOTE=mactec54;1334970]No we are not, I'm just showing the different options

You better look at some of the latest catalogs/white papers from the bearing companies. They do show two different types of dual AC bearings available.



[Quote]This is not correct the clearance can be adjusted, if fitted correctly, they will have Zero clearance in the bearing when fitted

Radial clearance yes, axial clearance no. The radial clearance can be changed by fit of shaft or housing but the axial can't. The variance in the grinding, is the axial clearance you have to live with. All of the bearing sites will give you charts with the accepted axial clearance in their bearings.

[Quote]Nothing special about them, I make them, they are just another Bearing style

So, you make your own bearings? There are more than one style of DRAC bearings. Not all of them are like you showed in post 20. Again you should look at some bearing sites.


[Quote]Not correct, when A/C bearing are assembled correctly, they will have zero clearance, no matter what type, If they do not then the Bearing will have a short life

So your saying that all AC bearings can be used in duplex situations, right out of the box? Don't think so. Again the bearing companies don't say this either. If they all can be used as duplex, why do they list two different kinds in the catalogs? I've got some that weren't listed as duplex(brand new FAG) that when the axial clearance is zero, the inner race is about .002 proud of the outer race on one side. When I complained to the supplier he said I didn't order duplex bearings. And then he told me what to look for.

You may know a lot, but you don't know everything.

[mactec54]

Packrat
Quote
So your saying that all AC bearings can be used in duplex situations, right out of the box? Don't think so. Again the bearing companies don't say this either. If they all can be used as duplex, why do they list two different kinds in the catalogs? I've got some that weren't listed as duplex(brand new FAG) that when the axial clearance is zero, the inner race is about .002 proud of the outer race on one side. When I complained to the supplier he said I didn't order duplex bearings. And then he told me what to look for.

There are more than (2) different kinds, in each series, you have to know what you are buying, all Bearing are ready to use out of the box, You just have to know how to use/ install them, & how they were made to be used, in your case it sounds like you got (2) standard bearings, You either have to make spacers, or grind them, very easy if you know what you are doing,

If you want to see some Tec information then I will give it to you, I don't have to go & read white papers, I know the Bearing Industry very well have been making custom bearing for more than 25years

Here is some information about the 5200/5300 series Bearings, & you can even buy them with zero clearance right from this manufacture, this is the only company that I have found that does offer zero clearance out of the box for this type of bearing

[Dixi5Price]

All of the bearing sites will give you charts with the accepted axial clearance in their bearings.

[packrat]

[QUOTE=mactec54;1335362]
Quote mactec
There are more than (2) different kinds, in each series, you have to know what you are buying, all Bearing are ready to use out of the box, You just have to know how to use/ install them, & how they were made to be used, in your case it sounds like you got (2) standard bearings, You either have to make spacers, or grind them, very easy if you know what you are doing,

If you go back and read my previous posts on this, it is what I've been saying all along. If you don't get the ones for duplex you need to make shims(my term)/ spacers(your term) both terms meaning the same thing.

[Quote mactec] If you want to see some Tec information then I will give it to you, I don't have to go & read white papers, I know the Bearing Industry very well have been making custom bearing for more than 25years

Here is some information about the 5200/5300 series Bearings, & you can even buy them with zero clearance right from this manufacture, this is the only company that I have found that does offer zero clearance out of the box for this type of bearing

Did you look at the chart you posted? It says nothing about axial(end) clearance. Only radial clearance. The only way to control that(axial) in a double row AC bearing is in the 4 point contact type you showed in your post #20. With two inner races ground to the correct fit.

[mactec54]

packrat
Quote
If you go back and read my previous posts on this, it is what I've been saying all along. If you don't get the ones for duplex you need to make shims(my term)/ spacers(your term) both terms meaning the same thing.

Shims & spacers are (2) completely different things


Quote Did you look at the chart you posted? It says nothing about axial(end) clearance. Only radial clearance.

You should post on subjects that you have knowledge in, because you have none in this subject about bearings

[LeeWay]

I think it has been over explained, but some good info in it anyway. I do think the initial question was kinda lost though.

That was how much more benefit can you get with AC's over regular bearings and thrust bearing combo's? I still think the answer to that is what kind of screw and nut you have. A single nut rolled ball screw will likely show no advantage with one over the other. Double nut or preloaded rolled ball screw may still not show significant advantage. Better screws than these probably will and then cost and budget would dictate how good you go. At some point you have to look at the ways and the rest of the machine and the products being produced to judge just how much money you throw at it.

I built my first mill and the table and saddle use nice THK linear bearings and NSK precision ground preloaded ball screws. Way overkill for the rest of the machine, however the bottom end works very well. The spindle is by far the weak link in that machine.

[mactec54]

Did you look at the chart you posted? It says nothing about axial(end) clearance. Only radial clearance. The only way to control that(axial) in a double row AC bearing is in the 4 point contact type you showed in your post #20. With two inner races ground to the correct fit.

The question packrat has asked about is Axial clearance, If you have a understanding how these Angular Contact bearings work, then you would know that if you have Axial clearance you will also have Radial clearance

So if you adjust the Radial clearance, the Axial clearance is adjusted as well, so the number you need to know to adjust these 5300 A/C bearings is the Radial Clearance, by controlling your shaft size, you can adjust the clearance to Zero, in both Axial & Radial

In the manufacture of angular contact Bearings the angle of contact on the inner race is the same as that on the outer race