Black Friday - MK4S kit Bearing issue
Putting this out there for any one else who might have just received there kit and came across a bearing issue. If something seems wrong with the bearing it might actually be bad.
After my Black Friday MK4S kit seemed to be stuck in Belgium for 7 extra days, it finally arrived and I couldn't wait to begin building. That was until I got to chapter 3 - the X axis and realized I had only one usable/passable X axis LM8UU bearing. Out of the 3, one was perfect, one was "ok", and one was like grinding your fingernails down a chalk board horrible. And this was just from sliding the bearing onto the rod, not even putting under stress or into the X axis assemblies.
My original MK3S+ sent me down the rabbit whole with bearings, but i read through all of the possible options and decided on "clean with IPA and then Pack your bearing with Super Lube #21030 grease". Have been running that forever with out issue. With the MK4S kit I figured maybe listen to prusa and use them as is. So just testing them on one rod my first bearing was smooth as silk, second had some chatter and the 3rd had something wrong.
I figured i would go back to what worked previously on my mk3S+ and cleaned them all with IPA and packed them with grease. This gave me two usable bearings but the third was just still horrible. I ended up ordering 2 replacement bearings from printed solid (much shorter shipping for me after the massive delay on the printer) that matched my first first silky smooth bearing. So if you are working on your new kit and a bearing just doesn't seem right or is way to noisy, go with your gut. With all mass produced parts there are going to be failures. This is nothing against Prusa as i know they source the bearings, but for someone new putting a kit together these problems can happen and for me I would rather get a new replacement bearing then a massively noisy printer and scored rod. Rather spend $5.99 per bearing then wonder what if.