Eccentric nuts on the top of the X axis

Hi guys

I’m having some issues on my s3.

I was milling some aluminium today - and was getting allot of chatter - after a minute it got so bad the machine spun out. Luckily nothing was damaged other than a clamp.

I went on to inspect and found my X axis carriage was loose - usually I would just rotate up the eccentric nuts - however after 360 degrees the V wheels were barely gripping.

I then took the whole carriage off - and tried to lower the top V wheels a fraction lower - with no luck.

I went on to replace the V wheels, eccentric nuts to no avail - whilst the carriage is on the tracks and wheels spin when you move the carriage, a finger gently on the wheel will stop it. Even on it’s tightest setting.

I’m at a bit of a loss as to what it could be - I’ve always struggled to tighten the x carriage wheels to a suitable tension. There is no obvious damage to the screw holes or the plate.

Any ideas?

I was wondering if I should fit eccentric nuts to the top of the carriage, but not sure if it’s a suitable/good idea.

I’ve emails C3D, but I figured I’d also ask you guys.

You replaced the bearings, too, right? Not just the wheels?

I’d replace top wheels/bearings if you haven’t and try that.

While you’re at it, make sure your steel belt pulleys aren’t touching the x-beam.


I had the EXACT problem, and did exactly what you did and got the SAME results…upon further inspection, I found that the belt guide bearings were rubbing against the aluminum extrusion. I removed the two bearings and OD ground them smaller (until they cleared the extrusion. The details are somewhere here in this forum. I’ll look for it and link it. Once I stopped the rubbing, the wheels got tighter and the carriage was tight.


I had enough up/down in the bolt holes to get the wheels off my extrusion. I am now able to slip two playing cards between the wheels and the extrusion.

I would have thought that having the wheels ON the extrusion would have tightened things, not loosened, though. Thus my comment above.

My steel pulleys were touching the X when I got the S3 a year ago. Since then no rubbing.

I haven’t replaced the bearings as yet, they seem ok

Ok, there is (was) too much variation in the V-Wheels back then, so next, I’d try swapping them out for wheels in other (Y axis) location. It’s called tolerance stack-up.

FYI: Before MY fix, I even entailed the thought of making some eccentric nuts with 0.036" offset (from annealed Allen wrenches). I even wrote the program, but never needed it. (I think the factory nuts are 0.028 to 0.031 offset)

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I have already swapped the V wheels?

Okay, responded in an official capacity, and ran this up the flag pole to the next level of support so we’ll see what is decided.

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Morning guys - I wanted to post a successful resolution and thank @WillAdams and support and the rest of the guys at C3D.

As everyone says support is first class. 8 days after posting this a new X/Z carriage has travels 3000 odd miles to me in England.

Whilst I had to dismantle and re-build my X/Z carriage, I can confirm this has resolved my issue. Interestingly my original one is of a different spec and I measured between the holes and found I had a slight difference - 0.9mm on the right and 0.7 on the left - compared to the new one sent to me.

It appears the original was slightly out of tolerance - that said it has been usable till late.

However what I’d like to highlight is the constant improvement I see from C3D. Whilst I do have an early revision of the Shapeoko 3, many companies would say this is good enough. Wait a year then knock out a new version. Not these guys! They improve and re-build their contents feeding improvements in from all sorts of places.

The original X carriage does the job very well, but the new version has multiple enhancements, such as fixed motors and tension bolt for the Z axis belt.

Now these enhancements might help with assembly but they also help give us a more rigid assembly that is easier to maintain.

So hats off you you! Thank you and I will post some pics when I have some time