help find:skatebearing replacements for $3-10

[vacpress]

So, the parts for my machine i am working on right now were supposed to get cut today, however i had to work and couldnt make it to school to get it going. As a result, I have an extra week for design tweaking..

I am looking for some ballbearings to replace my current proposed 'skatebearings' which I am using to hold my 3/8 to 1/2" ACME leadscrews. These skatebearings really are probably fine with some 'preload', but I am curious what else is a good choice..

I need 6, so cost starts to get sensitive for me, as I am a part time worker, full time tinkerer.

I am looking at this bay item:
http://search.ebay.com/search/search...tSearch=Search

i vaugely remember reading some great detailed threads about this, if anyone can help me find them.

thanks gaaaang.

[ger21]

You might have a problem finding small enough angular contact bearings. The 2 for $9.95 from VXB with the 10mm ID are the smallest I've seen for cheap.

[vacpress]

Gerry,

And they are affordable. I guess that at .4ish, they are allready too big for my leadscrew. Going to larger leadscrew is a real option in the future..

thanks for the opinion. I choose to trust it and order 2 out of hand to see if they seem that much better than the ABEC-7s.

Robert

[ger21]

On my Z axis (using skate bearings), I found that I can't preload the bearings much before they get stiff. They are probably plenty tight, but I'm guessing angular contact would work better. In the future, I think I' may try them out. It would be a bit simpler to turn the 1/2" acme down to 10mm instead of 8mm.

[massajamesb]

Don't know if you have tried here, but www.Vxb.com has all kinds of bearings....

[NC Cams]

Skate bearings are typically over runs or noise rejects of regular bearings of that same size. These are basically the bargain basement close out priced bearings that the bearing makers sell - they typically WON"T/DON'T/CAN'T get any cheaper unless you steal them.

Deeg groove ball bearings are NOT designed to take an appreciable axial load. Much more that 1%~2% of the radial capacity in preload causes the balls to "wedge" in the grooves in an area where they arent' supposed to nor are then designed to run. This explains why the phenomenon outlined in post #4 occurs

The skewed contact angle of A/C"s makes them suitable to run with an axial thrust - the higher the contact angle, the more thrust that they can absorb and still turn smoothly without failing.

They simply are NOT available in the small sizes that deep groove balls are. Due to the economies of scale (lower volumes and higher mfg cost) they are not/will not/can not be as cheap as deep groove ball bearings.

Wish as you might, that's pretty much what you're going to have to deal with.

[vacpress]

Mr NC CAMS,

Thanks for the reply... So the hope for a bearing that can take the axial loads in the $8-15/each range is sort of hopeless? I am sort of hoping that i can find a 'good deal' on ebay...

additionaly, ive got a lathe and can make inserts to allow larger bearings to hold my smaller leadscrews... In a way, this is a nice idea, as i could change to different or larger screws in the future, and feel secure that my $100/each ballscrews are resting in decent and appropriate bearings...

so, say i was willing to spend upto $25 on each, bearing, do you think that gives me some options?

Skate bearings are typically over runs or noise rejects of regular bearings of that same size. These are basically the bargain basement close out priced bearings that the bearing makers sell - they typically WON"T/DON'T/CAN'T get any cheaper unless you steal them.

Deeg groove ball bearings are NOT designed to take an appreciable axial load. Much more that 1%~2% of the radial capacity in preload causes the balls to "wedge" in the grooves in an area where they arent' supposed to nor are then designed to run. This explains why the phenomenon outlined in post #4 occurs

The skewed contact angle of A/C"s makes them suitable to run with an axial thrust - the higher the contact angle, the more thrust that they can absorb and still turn smoothly without failing.

They simply are NOT available in the small sizes that deep groove balls are. Due to the economies of scale (lower volumes and higher mfg cost) they are not/will not/can not be as cheap as deep groove ball bearings.

Wish as you might, that's pretty much what you're going to have to deal with.

[NC Cams]

When I need bearings, I buy what I need and shop for price if it is possible. However, for some items, you're simply going to have to either make do with something you can afford or fork over the currency that is being asked for the specific bearing you need.

Interstingly, NONE of the bearing application manuals and/or design manuals have $ factors in ANY of the load/life equations. When I did bearing application work, I'd design or configure something that would work (real important) - I'd then let the sales guy negotiate $'s with the client's purchasing people.

If you want hay, you pay one price, If you want hay that has already been through the horse, it is available albeit at a much cheaper price. Same stuff, slightly different "condition".

QUite often, what you can afford won't work, and what will work you can't/won't pay for or afford.

Your needs, your $$$'s, your call.....

[vacpress]

NC,

I have read a few threads about this topic which you were involved in. Your background seems impressive!

I totally know what you mean about the cost\benefit not always being the main equation. I use that mindset when I purchase music equipment.. Sometimes I want the better instrument.

These 5204, 5205 'angular contact bearings', are they worth looking at?
http://cgi.ebay.com/5204-ZZ-angular-...QQcmdZViewItem

Thanks for sharing your expertise.

When I need bearings, I buy what I need and shop for price if it is possible. However, for some items, you're simply going to have to either make do with something you can afford or fork over the currency that is being asked for the specific bearing you need.

Interstingly, NONE of the bearing application manuals and/or design manuals have $ factors in ANY of the load/life equations. When I did bearing application work, I'd design or configure something that would work (real important) - I'd then let the sales guy negotiate $'s with the client's purchasing people.

If you want hay, you pay one price, If you want hay that has already been through the horse, it is available albeit at a much cheaper price. Same stuff, slightly different "condition".

QUite often, what you can afford won't work, and what will work you can't/won't pay for or afford.

Your needs, your $$$'s, your call.....

[NC Cams]

I you want ZERO backlash, NO.

THese are a general purpose combination of radial/axial thrust absorbing capable bearing. They SUCK precision for ball screw use if you're trying to get a zero back lash system. You can get anywheres' from 0.001 to 0.005 backlash in EITHER direction depending on the clearance the bearing has and how tight you fit it to the shaft.

The ONLY way to get zero backlash is to use a preloaded A/C.

[Zumba]

The installation of a pair of A/C bearings is just as important as the design of the bearing itself. A sloppy fit of the outer race or improper preload will make it just as lousy as using the wrong type of bearing.

I'd say get the 5200 series double row angular contact and accept the fact that you will get a little bit of backlash. You can only expect so much accuracy out of ACME screws anyway. Will it really matter if you add another .002? These bearings are cheap as dirt.

The smallest size available is the 5200, 10mm ID. 5201 is 12mm ID and keeps going up from there.

[vacpress]

Thanks for the replies.

Factors like this make me wish i had designed this thing to use rack and pinion..