Z - Axis ACME Screw Guide

Good afternoon all! Just wanted to share a project I have been working on to improve the stiffness of the Z Axis.

The part sits on the spacers between the Spindle Carriage and the V-Pulleys, the hole in the center is designed to align the ACME screw. It creates another alignment point along the z-axis and improves the overall stiffness of the z axis, particurally when milling thru hard materials.

The hole is designed to fit over the screw tightly but no actual have no actual interferance.

After installing the piece I noticed a BIG improvement in z axis play/looseness.

Let me know what you think and any suggestions!

Part Files:

STL: X_Carve_ZAxis_Plate.stl (32.2 KB)
Parasolid: X_Carve_ZAxis_Plate.x_t (22.0 KB)
Autodesk Inventor: X_Carve_ZAxis_Plate.ipt (1.3 MB)


Thanks for sharing! I was literally just looking up to see what ideas people had for stiffening the Z.

Thanks, let me know if you end of making it or have any suggestions!

That surprises me. It seems that the ACME screw is responsible for lift, but not stiffness - that’s entirely the function of the roller wheels. Are you sure that when you installed the new screw guide you didn’t also maybe tighten the fit of the eccentric spacers of the Z wheels and that’s the improvement you noticed?

1 Like

I admit the screw is designed simply for lift but, looking at a free body diagram below, the “Cutting force” creates “Moment A” which are supposed to be restrained by the roller wheels.

But in my experience the roller wheels have a certain amount of play, even when properly adjusted. This lead to, in my opinion, the moment being transferred in part to the screw, and the default setup has only one mounting point, which allowed the z axis and cutting tip to “bend” in the x direction resulting in inaccuracies.

This new part is, in my opinion, helping the z axis remain vertical and increase the accuracy of the carves.

I may be wrong in my thinking and if anyone can help with a proper analysis that would be awesome!

I’m going to have to go out and do some wiggle tests now, but I’m less concerned about the moments about the Y axis (as pictured) and more concerned about rotations around the X-axis. I’m guessing those V-Wheels aren’t designed for such side loads, and the weight of a router hanging off a single plane of v-wheels seems like a fair amount of torque on the plastic Vs.

I’m getting good results, but it’d be nice for a number of reasons to get the feedrate closer to its theoretical sweet spot.

I have a bearing at the bottom of the ACME screw as well as at the top. Stops any flex in the screw.


Can you post a picture of your whole setup, that looks awesome!

The photo pretty much shows it all, the rest of the machine is standard X-Carve.
Plate takes a flanged bearing, same type as used in the top mounting plate. It’s screwed to the bottom of the Makerslide with a small spacer to compensate for the flange on the bearing.
Lower bearing plate is available here

One more reason to upgrade to a linear rail Z axis.

Really though, I agree. If I could start over I’d probably have rather just gone with a linear rail for Z from the get-go.


Fantastic, cheap, and easy upgrade! Thanks for sharing.

I downloaded the STL, which comes across in slic3r as teeny. Not a problem, I will download the Autodesk file and work with that. However, it might be worth fixing. Also, consider uploading this to Thingiverse - there are a bunch of XCarve mods.

Thanks again!

One down side of the bottom bearing on the Z-axis is that it reduces available clearance between it and the router bit/body.
Clearance between the router body and the bearing holder is just under 10mm which makes fitting a dust shoe like the Suck-It near impossible. Still working on a design to fix this.

Where did you find screw Gide ? I also need one. Please email me uttonken@yahoo.com

Hi @KenUtton,

We actually 3-D printed it in house.

If this is not what you went, my apologies, just let me know.


I ordered one of those plates last December and it never arrived. :frowning:

I did contact the seller a number of times but their customer service was not very good from my experience.

It was sent via post.

Interesting idea. now if you make that have a bearing in the 3d printed part it would be a nice cheap fix til that “Linear Z axis” comes in. :stuck_out_tongue:

Is there a link to purchase the linear z-axis upgrade? Thanks!

eBay is your friend in this case ,. Search for “linear z axis” . As I recall I spent about 150.00 +/- for mine and glad I did.

Awesome, will do. Thanks for the response.