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iMisspell
04-18-2015, 08:33 PM
Plan on replacing the gear box on my mill with a pulley system (http://bbs.homeshopmachinist.net/threads/66628-_-Looking-for-opinions-suggestion-experiences-and-insight-for-a-project).
As of now i will need 6 bearings for the pulleys and two for the spindle.
For the spindle i plan on buying the best i can afford/justify but for the pulleys i was thinking class 1 or maybe a better class of VXB bearing.

For the pulleys, what do you think ?

_

lakeside53
04-19-2015, 01:22 AM
Unless you buy Nachi from VXB, you'll just be getting generic Chinese bearings of dubious "class". Personally... I'd buy quality brand bearings.

macona
04-19-2015, 02:01 AM
Stick with something like a set of barden, timken/fafnir, or NSK angular contact bearings. You can often find NOS bearings on ebay, you want ABEC7 grade.

oldtiffie
04-19-2015, 02:33 AM
It may well be worth the OP going to the/a manufacturers web site and using their on-line bearing selection process to get the optimal (cost v performance v longevity) bearings for his job.

I doubt that ABEC class bearings are justified as the OP's work is pretty low load and not "industrial" high-load super-good bearing alignment on a 24/7 basis over several years with a very low probability of failure.

On that basis the bearings the OP and several others here recommend are likely to be very expensive whereas what or all that he really needs is a whole lot less as regards cost.

It may well be that iolite sintered bearings are adequate at least on/for some.

It probably doesn't matter if the bearings rattle around a bit - as long as the drives work well and are durable over a reasonable time.

But in the end its all up to the OP.

macona
04-19-2015, 12:00 PM
Oh. I thought he was replacing spindle bearings too.

If it is just for the idlers generic motor grade bearings will last you a lifetime.

iMisspell
04-19-2015, 12:53 PM
Thanks guys...


Oh. I thought he was replacing spindle bearings too.

If it is just for the idlers generic motor grade bearings will last you a lifetime.
I do plan on spindle bearings too, thoses will be of a high class/grade (like you suggested), but i was not sure about the bearings for the pulleys (idlers as you say). Was hoping/thinking the idler ones did not need to be of high grade, probably gonna go with low class Nachi from VXB or maybe high grade VXB branded.

mattthemuppet
04-19-2015, 01:54 PM
I just bought a bearing from vxb and found that for one or two it was cheaper to get them through vxb's eBay store. Sadly didn't fix the problem though :(

oldtiffie
04-21-2015, 02:50 AM
These might help with regard to ABEC (and other) bearings details:

http://www.engineersedge.com/bearing/ball_bearings_tolerances.htm

http://en.wikipedia.org/wiki/ABEC_scale

https://www.google.com.au/?gws_rd=ssl#q=abec+bearings

It is worth remembering that part of the requirements for best effect of those bearing sizes/tolerances is the "Class of Finish" of the finished shafts and holes.

Keep in mind that every time a bearing is placed or pushed/pulled onto its final surface that that surface diameter will be reduced in size for shafts and increased in size for holes as the surfaces are compressed and do not always return to the initial surface finishes or sizes when bearings are removed. Its not a lot at all and it may not matter - but it might.

Check the industry references and sources for details.

It may be well to consider the effect of compressed surface finishes if they affect the tolerances required as you may need to accept a down-grade if the bearing is replacing a same-size/class or else accept that you may alternatively have to accept replacing with a higher (next size) grade/class for getting the same performance.

Doozer
04-21-2015, 09:01 AM
Also remember basic bearing theory...
Rotating shaft, press fit the shaft, slip fit the housing.
Rotating housing, press fit the housing, slip fit the shaft.

-Doozer