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Swede,
Yes, if they are sold as a preloaded set, you do not need to fiddle with spacers. Just tighten them right tight against one another.
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Sorry to grab the unwitting with the thread title... in a way, I DID steal these! I'm looking for information from bearing gurus on their use and installation.
I purchased 6 or 8 of these paired sets for something like $12. They are New Hampshire BB precision angular contact ball bearings, packaged and designed to be used as a pair. Referencing the photo:
OD 32mm
ID 12mm
Duplex Pair
ABEC 7/9
BRG# ME-1201DM
I know a bit about ball bearings in general. Angular contact BB are typically used as a pair. Some of my own shop-made ballscrew bearing blocks make use of cheaper ($25 per BB) SKF 7200's, stacked with a spacer between the outer races, thus preloading the assembly when the ballscrew nut is tightened moderately. These higher quality bearings, like those found in a $250 NSK ballscrew fixed end, are stacked without spacers. The outer race is nicely etched with an arrowhead to show the direction of installation.
My question then, is this - Are bearing sets like these ground as a pair such that when the outer races are in contact, and the inner races loaded, then a certain level of preload is achieved, eliminating longitudinal play? If I were to use these with a ballscrew, how do I know when the ballscrew retaining nut is tight enough? In other words, when stacked without a spacer, do you simply cinch the retaining nut down firmly, and the precision ground inner and outer races deliver a calculated preload?
Any hints for installation and handling are appreciated. Thanks all!
Swede,
Yes, if they are sold as a preloaded set, you do not need to fiddle with spacers. Just tighten them right tight against one another.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
If you want, you can measure them with feeler gauges between the roller balls and outer race (free running measurement) and then again when installed and loaded, there are specs from manufateurers to tell you what "gap" is needed, Although HUng is right,you can tighten them right tight against one another.... some people wrench new bearings in and go overboard with the torque,you can put to much load on matched set bearings,,The arrows are indicating the direction of thrust.
Swede-
Where I work we use dozens of these bearing sets a day. (infact, these may be some that were "rescued" from the dumpster just to put on ebay. I've done it several times)
If the bearings are truly a match ground set, there will be "<" markings on the outer housings. These should be orientated so that they make a "<>" when matched up together. They should not need shims, and you should be able to clamp the inner and outer housings together, and have no axial play. I showed a picture of how to mount bearings like this in the pictures section.
http://www.cnczone.com/gallery/showp...cat/all/page/1
They are perfect for use with ballscrews and leadscrews.
Let me know if you need more. I've got at least a dozen pairs here.
Keith
Keith,
How do you keep track of those marks when everything is covered with grease, or obscured by shoulders or other bearings etc
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Hu-
Well, we only assemble shiny new parts.
Any of the ones that are greasy or have fingerprints go home with me!
The marks are found on the outer races, on the OD to be precise.
Seriously, the best way to assemble them is to start with everything clean, have the ballnut/leadnut bolted in place, but with the bolts loose, and the end of the ballscrew/leadnut hanging out of the end of the bearing housing. Then assemble the bearing on the ballscrew/leadscrew shaft, and tighten the locknut that clamps the inner bearing races together. Then slide the assembly into the housing that is a nice tight fit to the outer races, and then tighten a clamp plate that axialy compresses the outer bearing races. The bearing housing should not only be a nice tight fit, it needs to be aligned with the axis of travel. The play in the bolts that mount the ballnut/leadnut will take up the vertical and horizontal alignment. As I said, take a look at the picture I posted, as it matches with the text here.
Keith and all, thanks for the great info. I have 5 sets of these bearings, they are indeed of the uber-quality type with the "<>" markings. Still in the plastic wrap.
These bearings apparently sell new for over $100/pair! Keith, why do you go through so many?
We go through so many precision bearings, because we ship so many types of small to medium sized precision stages. This is a poppular size bearing that we use in a wide range of products. In fact, I have a pair of slightly used/new journaled ballscrews here that would accept the bearings that you have. The ends are turned and threaded to the priper size and length to accept those bearings. The screws would have about 22" of travel. Contact me if you are interested.
The product that we produce are at www.neat.com (hence the lame neatman name, I think homemachinist was already taken.)
The people in the stockroom and service know to see me first before throwing out precision components. I have finally trained most of them...
Keith
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