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[Closed] Misumi Replacement rods and bearings  

Active Member
Misumi Replacement rods and bearings

Hey guys, there is a lot of confusion about Misumi replacements and what to buy. I did a lot of research including googling technologies, scouring through blogs and forums, and email chains with Misumi. These recommendations might not be the best possible options out there, but I feel that they are the most beneficial at a reasonable price. I am making this as a new thread because the bearing recommendations thread that has been a little too contaminated with igus and other bearing discussions and this would probably get buried. (By all means, pick igus if your only goal is noise reduction. You should not see a print quality reduction from the stock bearings with them).

SFJ8-370 and SFJ8-330
(alternatively PSFJ8-370 and PSFJ8-330)

For misumi bearings, they encourage you to use a g6 tolerance. Many people are using the PSFU8-370 and PSFU-330 which in most cases should be fine. However, they have an h5 tolerance which isn't recommended by misumi to match their bearings. Another option is PSFJ8-370 and PSFJ8-330 which has the hard chrome surface like the PSFU8-370 and PSFU-330 but are at the correct tolerance of g6. The only advantages to the hard chrome are corrosion protection and a more appealing looking finish, but it adds cost.


On the forums, there has been a discussion about LMU8 vs LMU-N8. The difference is "with seal"(LMU8) and "no seal"(LMU-N8) I couldn't find too much about this online but Misumi strongly recommended sealed for 3d printing. Wikipedia just says that "Rolling-element bearings do not handle contamination well and require seals" so my guess is that all ball bearings should have seals and they sell them without seals for companies that seal them in their own way. But that's just a guess. If anyone knows the actual reason they sell without seals, please comment and I will update this page.

Upgrading Z axis:
I did not upgrade my z axis because I didn't sell the benefit. Compared to the x and y axis, the z axis hardly moves. If you intend to upgrade the a axis, just add two SFJ8-320 rods and four more LMU8 bearings.

This is what my order ended up looking like:

Posted : 01/04/2017 3:37 am
Jiojimbo liked
Eminent Member
Re: Misumi Replacement rods and bearings

Yep! I agree with your recommendation! I just posted this today about my upgrade with the exact same parts - except I did the Z axis as well.

I decided to do the Z as well since most of it would already be apart and the cost was fairly small for the extra bearings and rods. I did not want to have to keep in my mind that "my Z axis bearings/rods have ** number of hours on them but my X and Y only have ** hours". Also, I just kind of viewed it like only replacing 2 of the 4 tires on your car.

Posted : 19/04/2017 3:53 pm
Active Member
Re: Misumi Replacement rods and bearings

This is a great post. I started doing this research a while back, and after getting really down in the weeds, just decided to buy the MK2S upgrade kit to save myself the hassle (albeit part with more cash).

Do you know how your recommendations compare to the rods, bearings, etc in the MK2S upgrade kit?

Posted : 19/04/2017 11:30 pm
New Member
Re: Misumi Replacement rods and bearings

I'm curious as well about how they stack up to the MK2S bearings. I think my bearings aren't in great shape even with the printer being a week old as there is a definite resistance at one point in the movement of the bearings that is repeated as you pull the bed and I wouldn't mind an upgrade to make it more quiet anyway.

I was going to go ahead and order the bearings and potentially rods as well but it looks like Misumi no longer has their 30% off your first order promo going so that's $55 just in bearings or $35 skipping the Z axis.

Posted : 03/12/2017 10:08 am
Trusted Member
Re: Misumi Replacement rods and bearings

Does the MK2S use just one length bearing for all axes? Thanks

Posted : 03/12/2017 6:34 pm
Eminent Member
RE: Misumi Replacement rods and bearings

I have more than a year on my MK3S but its printing almost every day.  No sign of damage I am contemplating an upgrade for Misumi rod and Bearing. The y axis have to much play for my taste (not that i see direct problem, but from a mechanical point of view).  Anyone with those or similar care to share if it improve there print ?   Assemble with Grease and Clean/ re-grease every 6 months or so they should be good for a while....

  1. 10x LMU8 Misumi  
  2. 2x PSFJ8-320
  3. 2x PSFJ8-330
  4. 2x PSFJ8-370

Sorry to wake an old post i did post somewhere else more recent but maybe someone here can comment?


This post was modified 4 years ago by Frank_The_Rock
Posted : 08/05/2020 1:28 am
RE: Misumi Replacement rods and bearings

I did not order Misumi.  I ordered replacement bearings on Amazon and they have worked for a year.  I will probably replace them soon.  I have one printer with Drylin and the other standard bearings:

  1. 8 Pieces Igus Drylin RJ4JP-01-0812 PCS of LM8UU
  2. 12 PCS LM8UU


  1. 320mm x 8mm rods
  2. 330mm x 8mm rods
  3. 370mm x 8 mm rods

Not Misumi but I am very happy with them.  



Chuck H
3D Printer Review Blog

Posted : 08/05/2020 10:33 am
Estimable Member
RE: Misumi Replacement rods and bearings

Regarding sealed vs not sealed.....and don't forget Sealed For Life (SFL). Whether this is fact or a "truism" propagated by my materials science lecturer, or if things have moved on in the last 40yrs, this is my understanding.


The seal is to keep unwanted "stuff" out (told you it was 40yrs ago so they probably named the "stuff" by now) and prevent contamination of the balls, rollers or race. In our case that also includes the bulk of any grease we may wish to apply outside the bearing housing, on the rods say. Not saying none will get in just that it won't be very much and not do very much. The following is not a euphemism, although it is wee boy giggleworthy. If you have dry grindy balls a sufficient amount of lubricant must be applied to reduce friction. In our case we should have ignored the build manual and put some inside the bearing before inserting the rods...emoji of big sigh as I followed the book and not my head. Many sealed bearings which require regular lubrication generally have either seals that come off or a grease nipple 

Not sealed

Bearings not sealed are used either where their function/location inherently precludes foreign "stuff" getting to them or where you can readily get to them to clean them regularly. These are most often fitted with a cap as a dust cover and a seal on the other side. Grease is applied with a grease gun and after that has failed a brush.

Sealed for life

As the name implies you don't get into these. You throw them away at end of life. You can flush contaminants out with a light oil and this will have the dual advantage of removing the grease and leaving you with a very clean part with a new life expectancy of about....not very much. The actual revised life expectancy depends on load, speed etc etc etc but it generally rounds down to not very. If flushing is used you do get an added bonus, totally free and absolutely guaranteed. You get to wreck what the bearing was intended to protect....eventually....see definition above of not very for how long eventually is.

Hope that helps.




Posted : 31/05/2020 9:58 am