Low-Profile PCB Clamp for Genmitsu Cubiko CNC

I recently started experimenting with DIY PCB milling on my Genmitsu Cubiko CNC and quickly realised that most PCB holders online were designed for 3018-style CNC machines using aluminum extrusion beds and T-nuts.

The Cubiko instead uses a flat threaded bed with M5 mounting points, so many existing PCB holders either:

• don’t mount cleanly
• sit too high
• or waste precious Z clearance

While learning the PCB milling workflow, I came across this excellent PCB CNC tutorial by: Gomez Gimenez PCB CNC Tutorial. The PCB holder concepts there inspired this design, but I redesigned the system specifically for the Genmitsu Cubiko platform and low-clearance workflows.

This version:

• mounts directly using M5 screws,
• avoids 3018/T-nut dependencies,
• keeps the profile as low as possible,
• and securely holds PCB material during milling.

Included Parts

• Fixed holder
• Extended pivoting holder
• Printable thumb nut

Hardware Required

• M5 x 12 mm screw
• M5 hex nut

(Depending on your spoilboard thickness, longer screws may also work. I use them without one for maximum Z clearence)

Tolerance Variants

The thumb nut uses a press-fit hex cavity for the M5 hex nut.

Because fitment can vary depending on:

• printer calibration,
• material,
• shrinkage,
• and slicer settings,

I included multiple tolerance variants:

• 8.0 mm
• 8.1 mm
• 8.2 mm

The 8.1 mm version was tested successfully using Bambu Lab A1 with Bambu Basic PLA.

For best results, it is recommended to print the thumb nut variants first and test which fit works best for your printer/material combination.

A print profile containing all tolerance sizes is also included for convenience.

How It Works

The system uses:

• a fixed low-profile base,
• a pivoting extended arm,
• and a printable thumb nut with embedded M5 hex nut.

The arm rotates into position and locks the PCB in place while minimising vertical height usage — important on compact CNC machines like the Cubiko.