[handlewanker]

Hi.....I suppose the aspect of friction can be a double edged sword.........if a cage is not a friction item per se, then God didn't make small green apples.....the balls as they rotate do rub against the cage.....that is a friction fact, whereas an undersized ball between two balls does not.

Just for the example, if you have 3 balls in a line and the middle one is undersize by a smidgeon, the you have NO friction as the 3 balls can rotate in unison without rubbing against one another.

That is my opinion, and doubtless the fact that the manufacturers have gone to the expense of R&D with cages must mean something we are not to know about.

One thing that can't be overcome with smaller alternate balls is the reduced number of balls that carry the load

I don't think a linear bearing block with alternate undersize balls will ever fail in average use or with the heavier loading that some like to submit their machines to.

I don't intend to take my mill apart to get the balls out and test if they are alternate sizes or not........some things are too tedious to split hairs on, but if I were building from scratch and the balls in the bearing blocks were of the same diam then I would re-ball with alternate undersize balls as I think that it would be a better solution and cost effective.

Why would a manufacturer of a cheap ball nut have all balls of the same size when the alternate size method would work better (as in smoother) without extra cost.

More to the point, you won't get cages with rolled ball screws or no name linear bearing blocks so small alternate balls will score heavily in that direction.

I'll desist from arguing further on this one as no one has shown decisively that the alternate small ball method is a problem.
Ian.

[LeeWay]

None of the methods are a real problem. You are totally discounting the lubrication properties. The lube is the key. It can greatly extend the life of any of the items we have been discussing. In fact, it is probably part of the design from the very start. Lubrication diminishes the damage caused due to friction. If it didn't, then internal combustion engines would not be cost effective to operate. Parts do still have friction and wear, but the friction is low directly due to lubrication so the life expectancy is long in most cases, so acceptable.

[louieatienza]

Hi.....I suppose the aspect of friction can be a double edged sword.........if a cage is not a friction item per se, then God didn't make small green apples.....the balls as they rotate do rub against the cage.....that is a friction fact, whereas an undersized ball between two balls does not.

Just for the example, if you have 3 balls in a line and the middle one is undersize by a smidgeon, the you have NO friction as the 3 balls can rotate in unison without rubbing against one another.

That is my opinion, and doubtless the fact that the manufacturers have gone to the expense of R&D with cages must mean something we are not to know about.

One thing that can't be overcome with smaller alternate balls is the reduced number of balls that carry the load

I don't think a linear bearing block with alternate undersize balls will ever fail in average use or with the heavier loading that some like to submit their machines to.

I don't intend to take my mill apart to get the balls out and test if they are alternate sizes or not........some things are too tedious to split hairs on, but if I were building from scratch and the balls in the bearing blocks were of the same diam then I would re-ball with alternate undersize balls as I think that it would be a better solution and cost effective.

Why would a manufacturer of a cheap ball nut have all balls of the same size when the alternate size method would work better (as in smoother) without extra cost.

More to the point, you won't get cages with rolled ball screws or no name linear bearing blocks so small alternate balls will score heavily in that direction.

The plastic used for the "cage" are of an extremely low coefficient of friction. Nonetheless, there's always a touch of clearance to allow the lubricant to flow through.

Also, there definitely would be rub with the undersize ball, as it would be rotating at a different speed than the larger balls.

Manufacturers of cheap ball nuts DO put different sized balls in them, one because it is cheaper to not measure each ball, and two because they spin freer. But it's likely a more random process.

I'll desist from arguing further on this one as no one has shown decisively that the alternate small ball method is a problem.
Ian.

Promise?

[handlewanker]

Promise.....LOL....marriage is a solemn and costly promise and look where that gets some.

Just can't let this go as there are so many myths that seem to grow and add to the list of misconceptions.

One thing we'áll are forgetting......LUBRICATION......where does lubrication fit in when you have a long screw and a ball nut or linear bearing block that does NOT have a re-circulating lube supply like a car engine.

Once the scant supply of lube is wiped off along the screw or rail length the nut or bearing block is running on empty and that is as good as it will get.

Nobody...... (that I know of or are aware of) .......has yet fitted an air supply with oil mist injection to a linear bearing or ball screw to blow out any dirt before it can enter the mechanism and at the same time lube it continuously......many air tools have this feature mainly to lube them, but the application could be very advantageous for ball screws and linear rails.

At the same time, any lube that does get pasted manually onto the rail or screw immediately attracts swarf and other dirt particles that WILL get into any bearing despite the inadequate seals they are fitted with.

This has been well documented on many posts and is one problem for many failures of the same.

BTW, jut because a bearing is fitted with a cage to keep the balls apart does not mean the bearing will not clog up with any muck that is present from the work cycle.

I also doubt that manufactures of cheap ball screws and linear bearing blocks fit balls of miscelaneous sizes because they don't have access to graded balls that are available......if they have access to balls to fit their products it's thinkable that they could obtain ANY size to make their products perform well as in alternate ball diams etc.

If it was true that the cheepies had odd balls at random, then re-balling them would be cost effective to obtain a superior product.
Ian.

[NIC 77]

BTW, there are some cheap, as in very cheap, linear rails and bearing blocks sold on EBAY under the name BQLZR and they come with a plastic strip in them to prevent the ball falling out.
.

My really nice Bosch Rexroth runner blocks also have a plastic strip you remove. They pretty much all do.

I meant the spacer that slides into the block.

Same thing that I meant.

Although mine also have a synthetic cage for the actual balls.

Regardless of what is holding the balls in place, skewing the trucks during installation on the rails can drop balls. Even on nice big THK trucks. DAMHIKT.
For this reason, expecting to install the trucks as an assembly will not go very well.
THK and other have trucks with outer flanges for bolting the on from the bottom. If you are not designing for what you have one hand, then you can certainly get the trucks designed to meet your needs.
Not sure if Hiwin rails have that type of truck or not, but I would suspect they do.

If you use a little care when installing the trucks, there should be no issue.
Place some wraps of electrical tape around the other end of the rails. That may save a toe hit and ball chase.

Again, DAMHIKT.

Yeah it's not too big of an issue. You just need to be careful of the alighnment when you are putting them on and it's good to use a piece of rail when you bolt both bearings in place so that they will be aligned with each other before you try to slide both of them onto a longer rail. You could also insert the rail into the blocks then tighten them down, then mount the rail onto the machine. Also doing it in a place where if you loose a ball you can find it is a good idea. Easy enough to put a ball back in, but if you loose some balls, and can't find them again, how will you replace them?

[handlewanker]

BTW....I don't see ANY linear bearing blocks advertised on EBAY that have a plastic strip in them.....probably just for the photo......it's good to know that linear bearing blocks CAN lose balls like ball nuts do if you're not careful.

Edit.......after a close look at the photos the blocks on EBAY do appear to have a strip in them, otherwise you would be able to see the balls.
Ian..

[louieatienza]

Promise.....LOL....marriage is a solemn and costly promise and look where that gets some.

Just can't let this go as there are so many myths that seem to grow and add to the list of misconceptions.

One thing we'áll are forgetting......LUBRICATION......where does lubrication fit in when you have a long screw and a ball nut or linear bearing block that does NOT have a re-circulating lube supply like a car engine.

Once the scant supply of lube is wiped off along the screw or rail length the nut or bearing block is running on empty and that is as good as it will get.

Nobody...... (that I know of or are aware of) .......has yet fitted an air supply with oil mist injection to a linear bearing or ball screw to blow out any dirt before it can enter the mechanism and at the same time lube it continuously......many air tools have this feature mainly to lube them, but the application could be very advantageous for ball screws and linear rails.

At the same time, any lube that does get pasted manually onto the rail or screw immediately attracts swarf and other dirt particles that WILL get into any bearing despite the inadequate seals they are fitted with.

This has been well documented on many posts and is one problem for many failures of the same.

BTW, jut because a bearing is fitted with a cage to keep the balls apart does not mean the bearing will not clog up with any muck that is present from the work cycle.

I also doubt that manufactures of cheap ball screws and linear bearing blocks fit balls of miscelaneous sizes because they don't have access to graded balls that are available......if they have access to balls to fit their products it's thinkable that they could obtain ANY size to make their products perform well as in alternate ball diams etc.

If it was true that the cheepies had odd balls at random, then re-balling them would be cost effective to obtain a superior product.
Ian.

Most commercial machines have automatic oiler/greaser. The pressure forces the old stuff to basically ooze out.

Cheaper LM components have cheaper seals.

Balls are fitted to the ballscrew/ballnut. But in a rolled screw, they don't always put all the same size balls in, because they know at some point the ballnut will eventually seize. This is just due to the nature of how the ballscrew is formed. What happens then is that there will be torque variation required to drive the screw, and you may see that in the part, and It may be cyclical...

[LeeWay]

A clean white towel on a smooth work bench surface with good lighting, patience, container with some choice bearing grease, small container of cleaning solvent or degreaser, lock pick set or shaped awl set, jewelers screw driver set, magnet, tweezers, patience, micrometer, clean soft paper towels, a good plan, roll of tape and or zip ties and patience.
Why did I post this list?
This list can be the difference between success and failure when dealing with individual ball bearings.

[wizard]

Interesting direction (multiple) this thread has taken.

I might suggest that many of the points expressed are correct in one context or another. Consider this with refards to bearings in general thet can run without any lube at all. I can remember a division working with high vacuum processes that use to buy brand new bearings, take them apart and throw out the steel balls for plastic balls (probably ceramic these days). The idea of course was to eliminate any outgassing or other contamination avenues. In any event the point here is that sometimes plastics are the better solution especially when lubrication is a no no.

Like wise where i work now plain ole THK linear slides are run without lube in many location. These obviously dont last long at all even under intermittant duty and extremely light loads. In part you have excessive speeds being an issue. Even so steel on steel doesnt last in a completely lube free environment, the balls and slides end up looking like they have been attacked by a 4.5 inch grinder. So yeah lubrication is important and a significant factor in wear.

I bring this up because in most cases lubrication is your friend and almost anything helps. Where you start to have problems with lubrication is at high speeds. The wrong lubricant can lead to significant drag which impacts bearing life.

For most routers, staying with the simpler grease or oil solutions should be good enough. As long as your plastic or rubber (seals and the like) parts are happy with the lube you should get good results. Lubrication is important but not something to become obsessed with. Possibly the more important aspect is the lubrication program and sticking to a regular PM program that lubes but also cleans these components. The reality here is that if one forgets to lube a bearing it is certain to fail. This is perhaps also where automatic lube systems can be a problem as they make it easy to run a dirty machine.

[handlewanker]

Most commercial machines have automatic oiler/greaser. The pressure forces the old stuff to basically ooze out.

Cheaper LM components have cheaper seals.

Balls are fitted to the ballscrew/ballnut. But in a rolled screw, they don't always put all the same size balls in, because they know at some point the ballnut will eventually seize. This is just due to the nature of how the ballscrew is formed. What happens then is that there will be torque variation required to drive the screw, and you may see that in the part, and It may be cyclical...

Well that may be so for some suppliers .......maybe I got lucky when I bought a 1605 400mm ballscrew and a ballnut from different suppliers on EBAY...........this was to see just how good/bad it could get with odd stiff off the shelf at minimal cost.

I mounted the nut on the screw and ran it up and down a couple of times adding a bit of oil to the screw .......I couldn't detect any loose or tight spots over the entire 400mm length.

With time perhaps the surface hardness will wear unevenly and you would get loose spots, but as I advocated having two ball nuts fitted flange to flange with a resilient spacer, that would solve the problem and prevent any backlash in the bargain.....and if you're in a DIY hobby mode it's a bargain basement solution for that score that would pay dividends without compromise or breaking the bank.

I think that with cheap linear rails the alternate size ball fit will be the best solution to a cageless bearing......all balls of the same size without a cage makes no sense.
Ian.