[nicad]

I am wanting to build a "small" cnc chucker lathe from the ground up.
I have the spindle out of one of the 5C indexers, with a 45mm OD. I just got in some pillow block bearings (http://www.vxb.com/Merchant2/merchan...ategory_Code=), and they look like they might work with some preloading, but I have no data on the precision of the bearings. For that price, I am only expecting the lowest grade. :-/
Questions:
1) Anyone familiar with these 45mm pillow block bearings? They are simple deep groove type. Any preload/RPM suggestions? I would like to see around 3000rpm.
2) Are there taper roller bearings available anywhere with a 45mm ID? From what I understand these would be optimal, but I cannot find any anywhere!!

Thanks-
Colin

**edit typo***

[BEARINGMAN]

Those are a very CHEAP Chinese bearing with a LOT of play, they are single row deep groove ball bearings with no provision for greasing. If you feel you must use mounted bearings(pillow block or flange) then get a good brand- Koyo, NTN, KSK for Japanese, or SKF,FAG,INA for European. Do not use Fafnir(now Timken) because the locking collar can't stand reversing. If you can use a "naked" (unmounted) bearing, go for a sealed double row like a 5209-2RS. This will take the thrust loads plus the radial loads, while turning a a reasonable speed (4-5000).

[nicad]

Thanks for the information. Yeah I figured the pillow block cheapies were... eh, cheap.

I have found the 5209-2RS for $63.70/ea.
Is placing a set at each end of the spindle overkill?
What ABEC level would this bearing be considered?
Are there different manufacturers/qualities of this bearing number?

[NC Cams]

A 5209 is NOT a preloaded bearing nor can it be. Yes, it will accept bidirectional thrust but not without exhibiting radial and axial deflection/play/clearance in the process. If you want any form of radial and/or axial accuracy in a lathe, you need a preloaded bearing.

For a lathe, BIG, preloaded angular contact ball bearings need to be chosen. However a more affordable option might be to use tapered rollers.

In/around 45mm in ID size, there are over 2 dozen bearings with at bore size of 44.45mm to 46.038mm listed in the NSK catalog.

If you consult Timken, perhaps the world leading supplier of tapers, they may have even more - I don't have access to a Timken catalog.

Keep in mind that you don't simply choose bearings based on bore size, you do have to do some load life calculations if you want the thing to:

a. perform
b. live

Chosing bearings on SWAG's typically does not result in satisfactory performance and/or life.

BTW, tapered rollers offer perhaps the most radial capacity per dollar spent than any other option.

Find, dowload and consult a Timken applications engineering manual for the proper method for sizing and performing load life calculations for tapered roller bearings.

No time, interest or capability to do the necesssary load/life calculations? Chose something that is available and live with what you get..... good, bad or indifferent

And yes, pillow block bearings are ABSOLUTELY & TOTALLY UNSUITED for constructing a lathe spindle, regardless of who you buy them from or the country of origin. They are purely used/designed for power transmission where self alignment may be a pre-eminent requirement.

ABEC level needed is a function of what accuracy level you're trying to achieve in the peformance of the lathe.

Any "name" bearing supplier (SKF, NSK, NTN, Koyo, Fafnir/Timken, and many others) would provide bearings of comparable quality for a generic bearing. WHen you get into machine tool grade bearings, stick with the better brand names that are stocked at the local bearing supplier's warehouse. E-bay is not what I'd call a bearings supplier that one could "count on" when you reall NEED a bearing.

Caveat emptor when you go Ebaying for bearings.

[RICHARD ZASTROW]

nicad Ditto what NC said. I might add this. I recently had to price a set of PRECISION Timken taper roller bearings. They are more expensive than the same size angular contact ABEC 7 ball bearings. However, the Timkens take more load than the AC bearings. The AC's more speed.

[Geof]

How good or conversely how cheap do you want this machine to be? My first thought would be to use tapered roller trailer spindle bearings; very cheap, easy to get and replace. They may complain if you tried running them at 3000rpm all day; that is equivalent to about 200mph on the trailer.

[NC Cams]

IF you are going to SWAG it, you need to at least try to SWAG something that has some capacity.

If I were gonna SWAG, I'd look for "inner" front wheel bearings from a decent sized passenger car - say perhaps a pair out of a 1970 or so Cadillac "ambulance" package would be decent starters. Lots of capacity but I dunno about the speed rating. They should be fairly cheap and easy to come by at any auto parts store. You could affect a bit of preload with an appropriate retaining nut (ultra fine thread of course) on the drive end.

For a DIY lathe, these might be totally adequate (accuracy wise) if you ground the chuck mounting face and diametral register AFTER assembly. A good heavy duty wheel bearing grease might lube it for life. If you have a gear driven spindle and used APG 90-140 EP rated gear oil, this would lube both the gears and bearings if lubed from a common sump with a pumped oil system.

Better yet, consider some rear position pinion bearings out of a Ford 9" or a GM 12 bolt or a Dana 44 or Dana 60. I know that these have been run at 6-7" in racing appoications, especially the Ford 9" stuff and I doubt that you'll load them as hard/bad as a monster big block does on a drag car. Should be readily available but cost is $$$. They surely should be cheaper than a set of ABEC 7 machine tool bearings and/or a machine tool grade set of tapers from Timken. Besides, these can be purchased in kit form from Jeg's or Summit via mail order - hard to beat and better availability than dealing with Ebay.

Trailer bearings might be a bit on the small side, capacity wise.

Again, simply SWAG's are not the way I specify bearings but, I suspect that load info needed to do a proper load/life calc are non-existant at this point. Thus, if your gonna SWAG, use something that has proven durability in a horrible loading condition and a racing rear end pinion bearing is EXACTLY that.

There are LOTS of lathes built with standard grade tapers as opposed to machine tool grade bearings. Many of the imports are of that grade and no one seems to biitch too much about how these run/cut/perform.

The prior comments about SWAG's and load life calc avoidance still pertains so caveat emptor if you chose to build on "hunches" and "sage wisdom windage".

[nicad]

I have given myself about a $150 budget for spindle bearings.
I am now looking at pairing up some 40* angular contact bearings from McMaster (#6680K21)(ABEC-3) for the nose and a ABEC-3 deep groove to support the tail(#6661K111).

Or use an angular on each end of the spindle with a hefty pre-load spring washer? They would be spaced about 6" apart and I believe thermal expansion would alter non-sprung preload too much, right?

This lathe will be for brass/delrin/aluminum up to 1".

[gotis]

Well, if you want to go bigger I have 2 pairs of 7013 and 2 pairs of 7012 superprecisionbearings 4 sale.

FYI: these are 1350$/pair here.

I want 200$ /pair.


http://www.emersonbearing.com/SpecSh...erPrecison.pdf

[NC Cams]

From a capacity/thrust per dollar spent standpoint, you'd probably be better off with tapered rollers - especially if you're picking bearings out on "looks" and a $150 budget as opposed to actually doing load life calcs.

A wave washer may work to preload the bearings for an electric motor, BUT is TOTALLY unsuited to preload a bearing in a spindle to the amount needed for stiffness and precise cutting.

If you make both the spindle and the housing out of steel, the thermal expansion issues will cancel each other out and you can simply apply a position preload and move on with the project. This sort of thing is what they do on pinion bearings for an auto differential which is why this source of bearings was made in the first place.

If you look at Timken's catalog (especially at 1.75" - real close to 45mm), you'll find a HUGE selection of bearings to choose from that should suffice for a lathe. Besides, high capacity lathes quite often used tapered rollers so such useage is not ground breaking nor exceptionally novel.

Until/unless you can machine the housings with thee appropriate and properly defined concentricity, you won't see any of the benefit of ABEC 3's over garden variety ABEC 1's.

Besides, the higher the accuracy of the bearing, the LESS tolerant they are of 'off' conditions. Hence, if you're housing is not machined with concentric bores, the bearings are constantly trying to self align.

Thus, they can tend to experience chronic problems - cage breakage is a common malady in such instances, especially with ball bearings. Tapers encounter roller skewing which leads to shorted life and sometimes cage breakage.

Should the need be felt to point out at this point that this is a DIY project and NOT a rocket science project, I'm well aware of that already.

Regardless, there are right and deficient ways to do things - I'm trying to point out tried and true, proven technologies using my esperience and expertise as a former bearing applications engineer.

The member and casual observers are more than welcome to follow or ignore any suggestions and do things however they so choose - and live with the results however they may develop.

[nicad]

NC Cams-

Thank you so very much for the wisdom input. It may seem like I might be picking out bearings on a whim, but I am reading and gathering input to help make a "good" choice.

On that note, MotionIndustries has some very affordable 45mm ID tapered roller bearings in name brands.. like this NSK for ~$30 (Item #00131536).

Thanks again for the input, and anything extra you might have to say I am all ears.

[NC Cams]

The only advice I can give with regard to properly selecting bearings is that the designer of the system really needs to evaluate the load conditions and do appropriate load/life calculations.

When any bearing design work is done, the system geometry and the load and speed conditions are mandatory input factors so as to select the proper bearings for the give load and speed situations.

Any input that consists of "I dunno" makes it impossible to engineer the whatever so that it has the desired stiffness, durability and net performance being sought.

Consequently, "I dunno" also makes the choice of any bearing as good or as bad a selection as any other.

I can't help much with regard to bearing selection because I simply don't know the loads and speeds. Thus, all I can say is pick something with a lot of static and dynamic capacity and hope for the best if "I dunno" is/are the load conditions for your situation.

Since tapers are essentially shaped like cones, I can use emoticons to denote postioning. If you mount them like so:

> <

You would want to put a larger one (more capacity as opposed to bigger size) on the side of the chuck as this will probably see a bit more thrust and radial load.

IF you mount them as shown, feed the oil in from the smaller ID side. The bearings will tend to centrifuge the oil from inside to outside much more readily and/or naturally than if you try to shove oil in the big DIA side and have it come out the small side.

This mounting method is essentially EXACTLY the same as what is done on a pinion gear for a ring and pinion. Coincidentally, the pinion bearnigs have a need to both radially and axially position the pinion very precisely to maintian proper gear mesh - a condition you might want to duplicate in your situation.

BTW: distributor item numbers are essentially meaningless - when talking bearings, you need to use the industry number as opposed to some contrived stocking number.

The industry numbers are readily identififiable for speed and load capability - the "stock number" used by the distributor tells you nothing unless you go thru the hassle of translating it to an industry number.

Other advice: check out the Timken web site and download whatever you can with regard to using, fitting, mounting or selecting tapered roller bearings. Time and an educational effort well spent.

[BEARINGMAN]

NC Cams is 100% right on all points, but another way would be to mount them thusly >----<, one at each end of the spindle shaft. This way a nut on the drive end can be tightened for preload. One thing to think about is the efect of preload, tight=rigid, looser=faster. oil bath lube would be prefered.
All this said, if you aren't experienced enough to know all of this already, you are probably going to end up with a very expensive piece of scrap metal - better to buy a used spindle and rebuild it.