On my Prusa Mendel the x axis smooth rods are going non-level. Of the 4 M8 nuts, 2 of them have ridden up & one down, slightly out of their sockets in the motor holder & idler. Not fully out , but protruding by up to maybe 4mm. Seems worse on the top than the bottom. Also an intrmittent problem on z axis , motors whirr & maybe one in 10 times, no movement. Seems less of a problem when moveing down. Nuts & rods from the reprapkitstore, assumed to be steel. Using Z axis couplings by Nophead's design. After some searches, my plan is to dismantle the rods, run die on them to remove any burrs, then keep them lubricated with WD40. I've read that brass nuts not such a good idea , due to wear over time. Am I on the right lines? Anyone else had this ? (Alternative could be to drill/tap small holes in the motor mount & the idler a put small pieces of plastic to retain the nuts, however that doesnt have the right feel to it). Thanks in advance. Mike https://reprap.org/forum/read.php?1,122340,122340#msg-122340 Sat, 16 May 2026 08:06:56 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,122340,163900#msg-163900 https://reprap.org/forum/read.php?1,122340,163900#msg-163900 I found that the spring between the nuts was getting caught in the hole of the printed plastic part that retains the nuts and spring.
To overcome the problem, I took the assembly apart one side at a time, and with a small pair of pliers I opened up the spring diameter at each end a little, so now the spring has larger ends than the middle. This stopped the spring from entering the hole in the plastic part and also acted as a funnel shape at each end of the spring for the thread to travel in. No more binding and everything runs smoothly now.
I also changed the stainless nuts for brass nuts while I was at it.]]> regpye General Fri, 02 Nov 2012 02:56:53 -0400 https://reprap.org/forum/read.php?1,122340,123385#msg-123385 https://reprap.org/forum/read.php?1,122340,123385#msg-123385 Well the problem seems to have 99% gone away, but occassionally recurs, typically after printer just turned on. Might just be a need for more/better lubrication.]]> Anonymous User General Sat, 10 Mar 2012 09:11:05 -0500 https://reprap.org/forum/read.php?1,122340,123297#msg-123297 https://reprap.org/forum/read.php?1,122340,123297#msg-123297 I replaced the original nuts (steel?) with brass nuts.
Before fitting I ran an M8 die down both threaded rods and a tap in the brass nuts.
For lubricaiton I used what I had to hand, some lightish machine oil.

Early tests, but it looks ok.

Mike]]> Anonymous User General Fri, 09 Mar 2012 14:29:28 -0500 https://reprap.org/forum/read.php?1,122340,122676#msg-122676 https://reprap.org/forum/read.php?1,122340,122676#msg-122676 PastaRocket848 General Tue, 06 Mar 2012 15:23:33 -0500 https://reprap.org/forum/read.php?1,122340,122380#msg-122380 https://reprap.org/forum/read.php?1,122340,122380#msg-122380
Traditionally phosphor bronze nuts were used on lathes which is better. You can still get them if you shop around. They were generally replaced by brass due to the rising cost of bronze.]]> martinprice2004 General Mon, 05 Mar 2012 06:28:12 -0500 https://reprap.org/forum/read.php?1,122340,122373#msg-122373 https://reprap.org/forum/read.php?1,122340,122373#msg-122373 nophead General Mon, 05 Mar 2012 05:06:49 -0500 https://reprap.org/forum/read.php?1,122340,122369#msg-122369 https://reprap.org/forum/read.php?1,122340,122369#msg-122369
The idea behind using a soft brass nut on a hard stainless steel rod, is letting the nut wear out first since it's the cheapest to replace. With proper lubrication, it's been said the soft on hard metal actually might lead to less to no wear due to lower friction. I've used this combination on my latest Prusa for several months now, and there's no sign of the black "dust" I got on my Sells with steel on steel.

We've had many interesting discussions about this in the past, just search the forums.]]> Nudel General Mon, 05 Mar 2012 04:50:54 -0500 https://reprap.org/forum/read.php?1,122340,122366#msg-122366 https://reprap.org/forum/read.php?1,122340,122366#msg-122366
could self-locking nylon nuts be the solution? loctite? adjuster rings? drilling a hole into the nuts tapping a thread and inserting a lock-pin ? not through the rod, but just the nut, like on the adjuster rings.]]> Asger General Mon, 05 Mar 2012 04:19:58 -0500 https://reprap.org/forum/read.php?1,122340,122364#msg-122364 https://reprap.org/forum/read.php?1,122340,122364#msg-122364 ECSuyu General Mon, 05 Mar 2012 04:08:03 -0500 https://reprap.org/forum/read.php?1,122340,122356#msg-122356 https://reprap.org/forum/read.php?1,122340,122356#msg-122356 Asger General Mon, 05 Mar 2012 03:27:12 -0500 https://reprap.org/forum/read.php?1,122340,122355#msg-122355 https://reprap.org/forum/read.php?1,122340,122355#msg-122355 here in section 8 step 17 how the springs are used in a Prusa.]]> Sublime General Mon, 05 Mar 2012 03:25:17 -0500 https://reprap.org/forum/read.php?1,122340,122354#msg-122354 https://reprap.org/forum/read.php?1,122340,122354#msg-122354
[www.mendel-parts.com]

Does not look like it, but I am willing to adapt that design if it will solve my issue, though i have an excess of the adjuster rings so if they work i might as well use them instaed of having to go out and find/buy springs]]> Asger General Mon, 05 Mar 2012 03:21:13 -0500 https://reprap.org/forum/read.php?1,122340,122345#msg-122345 https://reprap.org/forum/read.php?1,122340,122345#msg-122345
Put one nut on the rod, then put the spring on, then push the rod with spring and nut into the X-end from the top (spring first) and put the second nut on from the bottom. Now push the rod all the way in the top so the spring is compressed and turn the bottom nut until it touches the bottom. Once you let it go the spring should pull the bottom nut up into the cavity.]]> Sublime General Mon, 05 Mar 2012 02:36:21 -0500 https://reprap.org/forum/read.php?1,122340,122343#msg-122343 https://reprap.org/forum/read.php?1,122340,122343#msg-122343
Can they just be replaced with adjuster rings? the ones on the inside of the frame at least, the top and bottom probably needs to stay]]> Asger General Mon, 05 Mar 2012 02:17:56 -0500 https://reprap.org/forum/read.php?1,122340,122340#msg-122340 https://reprap.org/forum/read.php?1,122340,122340#msg-122340 Of the 4 M8 nuts, 2 of them have ridden up & one down, slightly out of their sockets in the motor holder & idler. Not fully out , but protruding by up to maybe 4mm. Seems worse on the top than the bottom.

Also an intrmittent problem on z axis , motors whirr & maybe one in 10 times, no movement. Seems
less of a problem when moveing down.

Nuts & rods from the reprapkitstore, assumed to be steel. Using Z axis couplings by Nophead's design.

After some searches, my plan is to dismantle the rods, run die on them to remove any burrs, then keep them lubricated with WD40. I've read that brass nuts not such a good idea , due to wear over time.

Am I on the right lines? Anyone else had this ?

(Alternative could be to drill/tap small holes in the motor mount & the idler a put small pieces of plastic to
retain the nuts, however that doesnt have the right feel to it).

Thanks in advance.

Mike]]> Anonymous User General Mon, 05 Mar 2012 01:29:33 -0500