[pbrubaker]

Hey all,

I'm doing a machine rebuild right now, and I'm replacing the bearings in the spindle head since I have it apart. I'm kind of a noob with bearings so I could use some help. When I inspected the bearings, there are a few codes that are hand written/etched onto the outer ring of the bearings. I've done a bunch of digging into NSK's catalog and numbering system. I know what some, but not all of these mean. There are a total of 4 bearings. Two pairs separated by about 4". I am hoping some of you might be able to help out (especially with preload and clearance) so that I don't end up spending ~$1k on 4 paperweights.

Here are the numbers and a pic for clarity.

Bottom pair:
7014A DBBP4C8 CH NDH-669C NSK CK-107

Top pair:
7014A DBBP4C8 CH NDH-669A NSK CJ-57

I'm also considering switching to the 7014A5 (25 degree contact angle) bearing to increase the max speed a bit as I'm also replacing the motor. What should I consider when making such a change?

I'm considering these:

http://www.qualitybearingsonline.com/7014acdga-p4a-skf-precision-angular-contact/

Any help would be appreciated.

Pete

[the_gentlegiant]

Greetings,

Let's start here... do not change the contact angle on your bearings. Contact angles are very specific to the need at hand. Just replace with what exactly is in there. Even though I know a couple things about super precision bearings, neither of us knows enough about spindle design and engineering to change something as drastic as that. You don't mention what the spindle is out of or its top speed, but if you must get fancy, consider some manufactures "robust" series or ceramics. I think many basic designs can be had with a higher ball compliment, which may be stiffer, but may have other trade offs like noise and heat generation. Consult the manufacturer's literature concerning their alternate systems. If your bearings are greased, and you're trying to do something out of the ordinary, get them pre-greased, and/or pregreased and sealed. Handling and contamination from dirt of a hundred varieties is your greatest enemy in a spindle rebuild. Also check the squareness and condition of your precision lock nuts and that spacer you speak of. And any other clamp ring or spacer you may have. You'll typically have an outer race clamping flange on the nose end of your spindle. If anything, you may have to grind or machine to suit to get the clamping interference that is needed, because every set of bearings is going to have a different total thickness. There are another hundred and one things to know about what you're up to, but there are tons of great guides and manuals put out by the major bearing manufactureres to help you there. Consider getting a bearing heater too. Hammering is not allowed and slip fitting with heat is slicker than press fitting. Forget about selective fitting, which you'll read about. That's only for OEMs. I've yet to find a bearing supplier that will allow me into their back room to pick mine out of a batch. Many won't have a batch to pick from anyway. Hundred to one you'll end up with a "universal ground" bearing. Singular bearings ground to be used in any configuration and with any other of the same suit. The most you can do is try to match up the inner and outer ring diameter and width tolerances that are listed on the package. And use the markers on the bearing rings that list their points of greatest deviation. Many people don't have the measuring equipment of enough sensitivity to even find the small deviations in their shafts and housings. In that case, it's best not to line up all the ring markings, but differ them around the circumference evenly. Less likely to compound a problem that may or may not exist.

Just noticed some specifics in your original request. The clearence (guessing the C8) and preload are all built into the part number, so nothing to worry about there. Mostly when installing bearings with a taperd sleeve do you have to concern yourself with clearance/preoad. Correct me if you must but I don't think that's what you've got. One last word... clean your work area best you can before starting, and make sure you have the fitting and mounting tools at hand.

Finally. No really. From what I read, there is a big problem with counterfeit super precision bearings in the world market today. If you see some on ebay per say for a 5th of what you can buy them from a local reputable supplier, be afraid, because fewer statements are truer than, "you get what you pay for." Just sayin.

[pbrubaker]

Greetings,

Let's start here... do not change the contact angle on your bearings. Contact angles are very specific to the need at hand. Just replace with what exactly is in there. Even though I know a couple things about super precision bearings, neither of us knows enough about spindle design and engineering to change something as drastic as that. You don't mention what the spindle is out of or its top speed, but if you must get fancy, consider some manufactures "robust" series or ceramics. I think many basic designs can be had with a higher ball compliment, which may be stiffer, but may have other trade offs like noise and heat generation. Consult the manufacturer's literature concerning their alternate systems.

First, thank you for your detailed reply. I didn't mention the make of the spindle because it hasn't really helped me with any of my previous posts about the machine, so I figured I'd just stick to the details I was most concerned about. The spindle is a BT40 spindle from a Shizuoka B3-V. This spindle is the same spindle that is in the B5-V as well. Original specs were 6000RPM. I was hoping to take the speed up in the range of 8-10k max. The change of contact angle I was referring to was looking to see if 7014A5 (25 degree) would be a suitable interchange for 7014A (30 degree.) The specs are about the same between them but, I will consult an application engineer before doing anything like that. I will also look into the robust or ceramic options.

If your bearings are greased, and you're trying to do something out of the ordinary, get them pre-greased, and/or pregreased and sealed. Handling and contamination from dirt of a hundred varieties is your greatest enemy in a spindle rebuild. Also check the squareness and condition of your precision lock nuts and that spacer you speak of. And any other clamp ring or spacer you may have. You'll typically have an outer race clamping flange on the nose end of your spindle. If anything, you may have to grind or machine to suit to get the clamping interference that is needed, because every set of bearings is going to have a different total thickness. There are another hundred and one things to know about what you're up to, but there are tons of great guides and manuals put out by the major bearing manufactureres to help you there.

Duly noted. The existing bearings are open and greased. There is a seal on the nose and the rear of the spindle. The clamping nut is on the back of the spindle and it indeed clamps the outer race. There are two spacers between the two pairs of bearings, one on the inner race and one sized for the outer race.

Consider getting a bearing heater too. Hammering is not allowed and slip fitting with heat is slicker than press fitting. Forget about selective fitting, which you'll read about. That's only for OEMs. I've yet to find a bearing supplier that will allow me into their back room to pick mine out of a batch. Many won't have a batch to pick from anyway. Hundred to one you'll end up with a "univeral ground" bearing. Singular bearings ground to be used in any configuration and with any other of the same suit. The most you can do is try to match up the inner and outer ring diameter and width tolerances that are listed on the package. And use the markers on the bearing rings that list their points of greatest deviation. Many people don't have the measuring equipment of enough sensitivity to even find the small deviations in their shafts and housings. In that case, it's best not to line up all the ring markings, but differ them around the circumference evenly. Less likely to compound a problem the may or may not exist.

I was going to have the spindle taper ground, and the overall spindle checked out (tolerances and balance) prior to reassembly. I had planned to measure the spacers on my surface plate against a gauge block stack. I have a 0.00005" indicator, but maybe I'll just have the shop I send the spindle to look into that as well. Good tip on the bearing heater. I'll see if I can borrow one, or use a controlled high temp oven.

Also, what about the duplex universal grind? Would that be a better option?

Just noticed some specifics in your original request. The clearence (guessing the C8) and preload are all built into the part number, so nothing to worry about there. Mostly when installing bearings with a taperd sleeve do you have to concern yourself with clearance/preoad. Correct me if must but I don't think that's what you've got. One last word... clean your work area best you can before starting, and make sure you have the fitting and mounting tools at hand.

Yeah, I thought the C8 was the clearance as well, but I couldn't find any specs for it. I did end up getting some help over on an engineering forum with regards to the additional designations. NSK has designation document, that is incredibly hard to find. It was linked to me on the other forum.

https://drive.google.com/file/d/0B9H...xpQnlqNWs/view

This helped determine that the preload rating for the original bearings was medium. I will make sure everything is clean and I will do the assembly in a clean location.

Finally. No really. From what I read, there is a big problem with counterfeit super precision bearings in the world market today. If you see some on ebay per say for a 5th of what you can buy them from a local reputable supplier, be afraid, because fewer statements are truer than, "you get what you pay for." Just sayin.

I have purchased some eBay bearings for other stuff but I didn't intend to do that with spindle bearings. Thank you for pointing out the rampant counterfeiting problem. I'll make sure to source them from a reputable dealer.

Thank you again for your reply.

[the_gentlegiant]

I saw your postings over on PM concerning your spindle. I must say I like that machine you're working on. Never heard of it before. Kind of cool. Anyway... not sure you can get a spindle of that design up to 8 or 10k. Are those reduction gears or a drive for some other aspect of the machine? My point being, and I'm not sure about this, is I wonder if you can get that high of rpm with a belt or gear drive. Others probably know more about this than I. I think that duplex grind is just another term for two universal ground bearings sold as a set. Maybe they've matched the bores and OD's, I don't know. Sounds like you've got a good head on your shoulders, so I trust you'll get this all back together without too many problems. At least no more than can be expected when venturing out into new areas of mechanics. Couple last things... don't over grease if you do it yourself. Get a graduated syringe to do it with. Don't overheat the bearing. Usually you're wanting to heat only the inner ring. Don't re-call the temps to use but that info is out there. And finally, take your time breaking in those new bearings. Very important. Good luck with it all.

[lixingwen1987]

Luoyang Derun Precision Machine Tool Bearings co.,ltd.

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[jason003]

7014: angular contact ball bearing
A: 30 degree contact angle
DBB: 4 row matched like this //\\
P4: accuracy ISO class 4
C8: it seems like preload, special clearance

That's all I could find.