That clears it up - I've just never seen the / >< notation to indicate mounting arrangement. It seems the way to think about it is that < is a representation of the shape of the races, whereas the notation I'm used to, as shown on that KOYO page, represents the contact angle between the ball and races.
Ned Simmons
I think my ESM-59 is post 40s, and it did come with three bearings.
The first two of course are the angular contact pairs and take the radial and axial loads, the remaining one at the rear of the spindle is floating in the bore and takes only the pure radial loads of the end of the spindle.
Jim Schwitters was kind enough to send me a copy of hardinge's breakdown and replacement instructions for that machine - their nomenclature for the headstock was "Type R" for what it's worth.
Apparently the HLVHs use the two angular contact pairs with preload cylinder - likewise the DV59s?
So apparently hardinge went through the following design changes:
From collapsing cast iron shell bearings (on the cataract lathes) to three bearing setup (starting with the BB headstocks) and then at some time to two bearing setups after the 40s.
It would be interesting to talk to the engineers who decided how and when to make those changes.
Jim
From a practical standpoing however ball bearings are run with nearly zero clearance. What this means is that in either configuration, the name of the game is to get a rigid setup by making the clearance very near to zero in bb or ff (balls out, or balls in) setup.
Unlike tapered roller bearings, ball bearings don't respond well to large amounts of true preload.
Jim
Here's a good diagram of the different arrangemenats and their symbology:
The change from 3 bearings to two seems consistent with Hardinge KISS philosophy. By removing redundant constraints the 2 bearing design makes it easier to build a very true spindle at the expense of a bit of stiffness.
Ned Simmons
Except the OD marking on the figures on the right is backwards from Gunner's convention. To my way of thinking that OD marking is more consistent with the typical representation of angular contact bearings in the middle figures.
Ned Simmons
Yes, that would call for back to back mounting as illustrated in the link in Ned's post.
regards mark rand rtfm
It's not clear that the two bearing spindle is less stiff.
In the three bearing one, the last bearing runs true radial, and its outer races *must* be free to float inside the bore of the headstock. All the thrust loads are taken by the front duplex pair.
I suspect the main issue that lead them to three bearings was the differential thermal contraction rates between the cast iron headstock and the steel spindle. In principle the three bearing one does not suffer from any change in preload if the casting expands more than the spindle.
The other issue is there's no real precision item inside a three bearing headstock. The preload on the duplex pair is set in the bearing factory, and once installed will be developed correctly as long as all the races are up tight against each other.
In the HLVH though (for example) the preload depends critically on the separation between the bottoms of the bearing recesses in the casting, and the length of the 'preload cylinder' which is nothing more than a precision spacer that separates the two inner races. Maybe the engineers realized that the differential thermal expansion wasn't that much of a killer, and they could hire guys who liked cats and give 'em lots of Mt. Dew so they could do the tricky job of assembling the bearing stack through the headstock on the machines.
Because the spindle is constrained axially and radially by two bearings almost a foot apart that probably does make for a fair degree of rigidity. As opposed to having the backside only constrained by a radial bearing floating axially in a bore.
Jim
And the HC (chuckers), TFB (later ones..mine is an early 3 bearing machine), AHCs, DSM-A, CHNC etc etc
And most importantly..why those changes were made.
Indeed. All likely to be dead by now..sigh
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Way cool. Thanks for the link.
The OmniTurn CNC lathes use a spindle cartridge, with spring preload ..there are 8 springs pressing on a plate that presses against the back angular contact bearing. They too..are in the >< configuration, with a cylinder between them.
Im going to have to swap out a cartridge later this week. I tried to rebuild one from this particular customer several years ago...
The later Omnis use a low pressure air line to provide positive pressure on the spindle cartridge, to assist in keeping the coolant out of the spindle bearings. This particular shop is right next to the Pacific ocean..and until they finally listened to me...after years of pissing and moaning on my part..installed a high performance dryer at their air compressors..had a water issue with their air. To the point of the operators would regularly use their air guns to stage water fights in the shop.
When I pulled the cartridge and opened it up..it was a solid mass of rust. I have photos if anyone wants to see what water does to a $5000 spindle cartridge over a period of years....
So this one..which has had very very wet spindle purge air applied to it for years....Im simply going to exchange the cartridge...and let the rebuilder deal with it. Its gotta be grim inside....
Im also scheduled to do a spindle bearing replacement on a DV-59 tommorow. Hummm Ill ask the company if I can document the process with photos and post em for yall. They are a aerospace fastener company..so may be a bit..reticent. It would be nice to go along with that FAQ I wrote a few years agon on the process.
The DV-59 will be nearly identical in process as the HC chuckers, etc etc.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Yes - 7000 series are angular contact
A simple way to identify face and back is to think of the bearing as a baseball cap. Look at the Koyo site posted earlier (
Be careful that you buy only from an authorized distributor regardless of which brand you choose. There are bargains out there from "gray market" outfits but the manufacturers will not honor any warranty or provide any service.
>
some bearings just use a dot or circle to mark the alignment points. It depends on the manufacturer.
John
Can anyone describe which face is the ">" and which is the "
I tried to find a good .html picture for you but couldn't. If you go here to the Barden site and look at page 13 of their "Machine Tool Catalogue" you'll see a very good diagram of the different arrangements:
Also found info that says "The DB arrangement requires the inner rings to be clamped whereas the DF arrangement requires the outer rings to be clamped". It's on the NTN site here at the bottom of the page:
After sifting through the Yahoo posts and getting more confusion from reps at the manufacturers I figured it would make a good topic here, thanks!
BTW I went with a pair of Barden 205HCDUL which are 15 degree contact, duplex mounting with a light pre-load :)
More pix of my restoration here, getting ready to paint soon...
An overhung load applied at the spindle nose creates a moment that needs to be balanced by the spindle assembly. In the two bearing spindle that moment is resisted by the widely spaced bearings, causing the spindle to bend between the bearings.
With the three bearing spindle, the angular contact pair at the nose not only provides radial and axial support, but also resists the moment that results from the overhung load. In addition, with 2 bearings at the nose, the total radial stiffness of the bearings themselves is greater close to the load. Clearly, since there is some angular deflection of the spindle as it passes thru the bearing pair, there's also a bending moment in the spindle between the front and rear bearings, but it's smaller than with two bearings, and adds to the resisting moment provided by the pair at the nose.
No doubt that's one reason that bearing arrangement is so widely used.
I'd expect to find there's both an inner and outer spacer, match ground, though the outer spacer may be fixed in the spindle cartridge.
I hear those guys work cheap, too. I wonder if the 3000RPM top speed of the HLVH is a consequence of the the bearing spacing. I often wish my Feeler would turn faster. Likely the permanent grease lube is a limiting factor as well.
As long as the angular contact pair is carrying the thrust loads, the fact that the radial bearing is floating axially has no effect on its ability to carry a radial load. A bigger issue is the fact that a single bearing will inevitably have some small amount of radial clearance, so it's likely that light loads at the nose may not load the rear bearing until its clearance is taken up. This is likely one reason it's common to see a preloaded axially floating pair at the back end of a spindle in place of the single bearing.
Ned Simmons
Gunner will no doubt correct me if I'm wrong, but my understanding (based on his overhaul instructions) is that the outer races are separated only by the headstock casting. These machines do not have a 'cartridge' per se. The rear bearing comes out the back, the front one comes out the front.
My real concern is that for the rear radial bearing to float, it must have some non-zero clearance in the headstock bore. Even if small it is present and will serve to reduce the rigidity of the *rear* of the spindle. The BB headstock machine I overhauled had the rear bearing fitted snugly but I was able to extract it without resorting to heroic measures.
I am not certain but the instructions that Jim Schwitters sent me for the more modern "R" type headstock imply that there is a sort of preload spring for the rear bearing. I did not disassemble the machine far enough to see that, I was only trying to verify the state of the lube inside the three bearings.
Jim
Thanks - I should be able to figure it out now.
It's looking pretty good - when do you think you'll have it all up and running? I've only stripped down and repainted two tools (a shaper and a die filer) and both took me far longer than I expected. Brush painting seems to take forever, especially with a couple of coats of primer and top coat.
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