Nice, a round version is a good addition. Here's the full updated post with both variants covered:

Desk Clamp Stabilizer Plate

Short Summary "Stops your desk clamp from slowly walking off the edge. Mounts under the desk, clamp disk sits in a recessed pocket and stays put."

Summary

If you use any kind of desk clamp (cat perch, mic arm, monitor mount, etc.) you've probably noticed it slowly walks its way across the desk over time and eventually off the edge. This plate fixes that by giving the clamp disk a recessed pocket to sit in, keeping it locked in one spot on the underside of the desk.

The plate mounts to the underside of your desk with 4 countersunk screws. The clamp disk drops into the pocket and can't migrate anywhere, no matter how much load or movement is on the clamp.

Two versions included: square and round. Same function, just pick whichever suits you.

Files

Includes ready-to-print STL and 3MF files for both the square and round versions, sized for my specific clamp (35mm disk). These will likely need adjusting for your clamp. Open the .scad file, update the disk diameter and thickness at the top, and regenerate for your own setup.

Details

Square version:

• 120x120mm plate, 18mm thick

• Screw holes 20mm from each corner

Round version:

• 140mm diameter plate, 18mm thick

• 4 screw holes at 90° intervals, 20mm from the edge

Both versions:

• 35.5mm pocket diameter (35mm disk + 0.5mm clearance)

• Pocket depth captures the full disk thickness

• 4x countersunk M4 screw holes

• Fully parametric in OpenSCAD

Print Settings

At least 4 perimeters and 30% infill recommended since it takes the clamping force directly. No supports needed.

If you adjust the parameters so the pocket goes all the way through the plate, you can drop the infill a bit since the walls are doing most of the work at that point.

Customization

Open the .scad file and change the values at the top to match your clamp's disk diameter and thickness. The plate and pocket regenerate automatically.

My Make

Printed in black, mounted to the underside of a wooden desk. The clamp disk sits fully inside the pocket flush against the desk, held in place by 4 countersunk screws. The C-clamp threads up through the pocket and tightens with the ball-end knob as normal. No wobble, no creep. Exactly what I needed.