I need to add grease to my linear bearing blocks but the fill hole seems to be sealed. What am I missing?

For my DIY build I bought these MGN15H linear guide rails via AliExpress. So they probably are no quality brand. That being said: I wanted to add lithium grease using a syringe via the center hole. But it looks like these holes are sealed (green paint). How should I add the lithium grease?

The hole does not contain a plug or screw. What obvious thing am I missing?

It’s a good shot, but still can’t really see…


There wasn’t really any information on if these are ‘lubricant’ holes or not. You photo appears that some of the lubricant is coming out of the hole.

Is it plugged?

Sealed? Looks like some lubricant is coming out of that hole.

I just put lubricant on my rails, that’s a guaranteed. Before I changed out the head, you couldn’t get near the bearing.

Other bearings on that site have a zerk fittings on them, these don’t show it.


No there isn’t lubricant coming out of the hole. It’s shiny green pain reflecting the light. :man_shrugging:t2:

I’m not 100% confident it’s the lubrication hole. But if it isn’t the lubrication hole I wonder what the correct lubrication method is.

Of course I can just add some grease to the rails. And I’ll probably just end up doing that. But just out of curiosity I’m trying to find the ‘official’ method for my bearing bocks.

Did you go to that link? You can ask them…

I couldn’t find a ‘data sheet’ of any kind on that site. That might be worth asking them for. It will tell you…

Good luck.


I asked my Ali express seller. If I don’t get a response I’ll try your site. I’m not sure if it’s a genuine product so I feel kind of bad asking the original producers of the product.

If I find out the ‘official’ way I’ll report back.

I wouldn’t let it bother me. If they are selling knock offs maybe the manufacturer needs to know.

Maybe they are legit and you are hurting yourself.


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