Blog › Rods, tubes and profile rails: what the axes slide on
1 November 2026 · 2 min read
Rods, tubes and profile rails: what the axes slide on
The guides that keep each axis straight come in a few shapes. What the makers in the record say they use.
The screw pushes an axis along; something else has to keep it straight. That's the job of the linear guides, and spec sheets describe them in several ways: linear shafts, steel tubes, profiled linear rails, or V-wheels running in an aluminium extrusion.
What each maker says
| Machine | Linear guides, as published |
|---|---|
| SainSmart 3018-PROVer V2 | Linear shaft |
| SainSmart 3020-PRO MAX V2 | Dual steel X-axis guide rail; Y and Z not published |
| SainSmart 4040-PRO | Not published |
| FoxAlien Masuter Pro | Linear rails on Z; X/Y not published |
| FoxAlien Masuter Pro Max 2x2 | Not published |
| SainSmart 4040-PRO MAX | Linear rails on X and Z (X described as a "linear optical axis rail") |
| Onefinity Apprentice | 30 mm hardened steel tubes X/Y; 16 mm guide rails Z |
| FoxAlien Masuter 3S | Dual HG-15 linear rails on Z; the page also mentions a "steel wheels pulley system" without naming the axes |
| Sienci Labs LongMill MK3 30x30 | 15 mm profiled linear guide rails, all axes |
| Onefinity Gen 2 Elite Woodworker | 60 mm steel tube X, 50 mm Y; 20 mm guide rails Z |
| Carbide 3D Nomad 3 | HG15 linear rails on Z; X/Y not published |
| Sienci Labs AltMill MK2 4x4 | HGR15 linear guides on all axes |
| Carbide 3D Shapeoko 5.1 Pro 4x2 | HG-15 linear rails, all axes |
| Sienci Labs AltMill MK2 2x4 | HGR15 linear guides on all axes |
The descriptions aren't consistent enough to rank. Some pages describe all three axes; others describe only Z, which is often where a maker has upgraded. FoxAlien says the Masuter Pro's Z axis uses linear rails "replacing the optical axis", and Carbide 3D says the Nomad 3 has "HG15 linear rails on the Z-axis" without describing X and Y.
Reading the codes
Carbide 3D writes its profile rails as "HG15" or "HG-15". Sienci Labs describes the LongMill's as "15mm profiled linear guide rails and bearing blocks on all axes". Onefinity gives tube sizes instead: 30 mm hardened steel tubes on the Apprentice, 60 mm and 50 mm tubes on the Elite.
The drawing above is a simplified guide to what the words describe. It isn't a claim about which kind is stiffer or lasts longer; none of the makers' pages give comparable figures for that, and this site doesn't test machines.
Sources
Read on 1 November 2026. Quotes are copied from these pages.