Conduit, Rails, Tubes, Pipes…

Recommended Starting Size

This CNC runs on inexpensive thin walled galvanized steel conduit found in 23.5mm, 25mm, 25.4mm Outside Dimension (OD). Stainless steel tubing (wall thickness approx .049″-.065″) is a good upgrade that increases rigidity and accuracy.

In the US 3/4″ thin walled EMT fits the 23.5mm parts, 3/4″ refers to the Inside Dimension. The price for conduit is about $8 US for the ~20′ needed.

Very large builds are possible, if the outer rails are supported along the span. The smaller the machine the more rigid it will be, the faster you can push it. I recommend starting with a foot print of  24″ X 24″ Outer Dimensions with a 3-4″ usable height.


Cut Calculators

Inspired by GeoDave and SteveCD, I gave it a shot.




Z Rails should have 5-8mm holes drilled 22.5mm from the bottom and and 75mm above that. If your nut traps don’t fit your rails thickness well Geodave made a nice parametric part here,



File or sand down the inner and outer sharp edges left after cutting! Sharp edges make assembly difficult and can damage your wires. I have one of these and It was worth every penny.


Sample Cut list

3 Rails X  = Usable Width +264mm (10.4in)

3 Rails Y  = Usable Depth +264mm (10.4in)

2 Z Rails = Usable Height + 190mm (7.5in)

4 Legs = Usable Height – 13mm (.5in)

1 Lead Screw (T8) or Allthread = Usable Height + 76mm (3in)

Table will be 6.5mm (.25in) longer in each axis direction. (30in X rail will need a 30.25in table in the X direction).