Why there is play in lm8uu based linear rail , I measure the diameter of different roads all diameter is less than 8mm it's around 7.6 to 7.8 mm is it common tolorance or perfect 8mm rods are also available??
That sounds suspiciously like 3/10 inch rods. Almost all the rods i've come across are in even millimeters, the cheap rods i'm using for these bearings are within 100th of a millimeter of being 8mm, so 7.99-8.01mm
To have a linear bearing where the rod can rotate you would either need a sleeve bearing, or you would mount your linear bearing inside one or two normal axial (rotating) bearings. Rotating the rod in the bearing above would cause excessive wear on the balls, races and rod because the balls can't roll in that direction.
You should consider seeing if this can be pinned in the Discord...was a huge help for me after cleaning and packing my bearings. I lost some of the balls in the process (1.5mm?) and needed to reassemble the bearings to ensure proper pre-load. Probably overkill, but I want quality in my build.
How do I make these roll smoother? I have two that are brand new and pretty rough with a little weight (5lb maybe) . I tried packing with grease and it didn't help. I then took them apart, cleaned and reinstalled. No change. I tried leaving 1 bearing out per race for a little extra room in case they were binding and it's still the same. What else can you do? Sand the housing surface smoother where the bearings make contact?
This could be caused by a couple of things. Your rod might have the wrong diameter or be too rough, the bearing races (the polished tracks that the balls roll on inside the bearing) might be too rough or the return path might be rough or not lined up properly. Considering these are about €2 i would primarily try to get some new ones to see if they would work better.
Imagine doing it in a homemade way with pvc tube and bicycle bearings. The only question that remains is how to make the center basket so that they do not get lost.
The basket is quite simple, it's basically an oval track in a plastic tube that fits between the outer tube and the rod. The really tricky bit is how you cut out the deeper tracks in the tube and keep the basket centered on that track. Without that deeper track the balls can't circulate back to the beginning again.
They would have to be since people will be lubricating these with many different lubricants. They won't be very mechanically durable though. Not that it matters with these cheap bearings since it turns out the ball races are made from fairly soft steel. Only a few hundred thousand operations at fairly low load deformed the races enough that the balls started jamming up and stopping.
You can't rotate the plastic to spread the wear since the return paths are cut as grooves in the bearing surface. If you look when i show the inside, the bearing surfaces are cut as a slight groove to keep the balls rolling straight when under load, if you didn't do that they would start eating in to the carrier very quickly, especially these plastic ones. I did wear one of these bearings out, it started scraping after only something like 800k operations under moderate load, the bearing surface turned out to be way too soft so it wore a groove in it so the balls started pinching and no longer rolled.
I'm not sure which part of the machine you would use this on. In either case these 8mm bearings can take more static load than the 8mm rod they would be put on. The cheap Chinese versions will wear out after a few hundred thousand operations though. Maybe look at the 12mm version since that should handle a lot more wear without seizing up.
@@Ghlargh if you've ever seen a weight stack, I presume he's referring to the same sort of thing. With a smith machine the weight is fixed so that it can only move up and down (as permitted by the linear bearings).
Unevenly, it's a dirt cheap mass produced knock-off after all. I think the one i took apart had an even number of balls but i would not be surprised if some of them are missing a couple. At least the double length bearings should work fine with one or two balls missing per race.
Why there is play in lm8uu based linear rail , I measure the diameter of different roads all diameter is less than 8mm it's around 7.6 to 7.8 mm is it common tolorance or perfect 8mm rods are also available??
That sounds suspiciously like 3/10 inch rods. Almost all the rods i've come across are in even millimeters, the cheap rods i'm using for these bearings are within 100th of a millimeter of being 8mm, so 7.99-8.01mm
@@Ghlargh I purchased from two Sellers both are almost similar in tolorance one was 7.6 and other 7.8 very loose on bearing.
From Amazon.
it's so simple yet so smart, as all things should be
Thank you for this. As well as going along a rod, could the rod turn in it instead?
To have a linear bearing where the rod can rotate you would either need a sleeve bearing, or you would mount your linear bearing inside one or two normal axial (rotating) bearings.
Rotating the rod in the bearing above would cause excessive wear on the balls, races and rod because the balls can't roll in that direction.
You should consider seeing if this can be pinned in the Discord...was a huge help for me after cleaning and packing my bearings. I lost some of the balls in the process (1.5mm?) and needed to reassemble the bearings to ensure proper pre-load. Probably overkill, but I want quality in my build.
How do I make these roll smoother? I have two that are brand new and pretty rough with a little weight (5lb maybe) . I tried packing with grease and it didn't help.
I then took them apart, cleaned and reinstalled. No change. I tried leaving 1 bearing out per race for a little extra room in case they were binding and it's still the same.
What else can you do? Sand the housing surface smoother where the bearings make contact?
This could be caused by a couple of things. Your rod might have the wrong diameter or be too rough, the bearing races (the polished tracks that the balls roll on inside the bearing) might be too rough or the return path might be rough or not lined up properly.
Considering these are about €2 i would primarily try to get some new ones to see if they would work better.
Imagine doing it in a homemade way with pvc tube and bicycle bearings. The only question that remains is how to make the center basket so that they do not get lost.
The basket is quite simple, it's basically an oval track in a plastic tube that fits between the outer tube and the rod. The really tricky bit is how you cut out the deeper tracks in the tube and keep the basket centered on that track.
Without that deeper track the balls can't circulate back to the beginning again.
It's actually Nylon 6 or 66, it's very durable and resistent to lubricants, solvents and petroleum based products.
They would have to be since people will be lubricating these with many different lubricants. They won't be very mechanically durable though.
Not that it matters with these cheap bearings since it turns out the ball races are made from fairly soft steel. Only a few hundred thousand operations at fairly low load deformed the races enough that the balls started jamming up and stopping.
Seems like these would have a long lifespan as long as the plastic rotates so that the wear is distributed over the entire inner surface area.
You can't rotate the plastic to spread the wear since the return paths are cut as grooves in the bearing surface. If you look when i show the inside, the bearing surfaces are cut as a slight groove to keep the balls rolling straight when under load, if you didn't do that they would start eating in to the carrier very quickly, especially these plastic ones.
I did wear one of these bearings out, it started scraping after only something like 800k operations under moderate load, the bearing surface turned out to be way too soft so it wore a groove in it so the balls started pinching and no longer rolled.
A co insidense this video poped up just after I took apart my bearing. And half of the balls was spread over the floor. Haha
'crowns'? Whats that?
Can this be strong enough to be used on gym smith machines?
I'm not sure which part of the machine you would use this on. In either case these 8mm bearings can take more static load than the 8mm rod they would be put on. The cheap Chinese versions will wear out after a few hundred thousand operations though.
Maybe look at the 12mm version since that should handle a lot more wear without seizing up.
@@Ghlargh if you've ever seen a weight stack, I presume he's referring to the same sort of thing. With a smith machine the weight is fixed so that it can only move up and down (as permitted by the linear bearings).
So it looks like there is no adjustments available
I’m trying to put mine back together... there are 94 balls and 4 slots, how do they divide?!?
Unevenly, it's a dirt cheap mass produced knock-off after all. I think the one i took apart had an even number of balls but i would not be surprised if some of them are missing a couple. At least the double length bearings should work fine with one or two balls missing per race.
Thank you for this video!
Many thanks
Hahaha. This is great!
I was expecting covfefe to be inside ! Not ballbearings
Funny you'd say that....
ruclips.net/video/4u_CNm1Lk7A/видео.html