Pen Centering Cones + Gridfinity Holder – For Long‑Shaft Fine Pens

This set contains two 3D‑printed centering cones designed to help you accurately mark the center of existing holes using a fine pen or marker. Perfect for woodworking, metalworking, drilling layouts, wall mounting, construction work, and general workshop marking tasks.

If you’ve ever tried to mark a hole with a pen that doesn’t sit straight, you know how frustrating it is. These cones solve that problem by guiding the pen shaft perfectly into the center every time.

I couldn’t find a proper tool for centering long, thin pen shafts, so I designed my own — and now you can print them too.

Included Models

✔ Two centering cones

Two variants with different outer diameters for max 8 mm and 14 mm holes, height is 15mm, suitable for both small and larger holes. Optimized for pens and tools with:

• shaft diameter ≤ 2.5 mm

• shaft length ≥ 15 mm

Compatible with fine‑liners, technical pens, center pens, mechanical pencils and other long‑shaft precision tools.

✔ Gridfinity storage bin (1×1)

Both cones fit neatly into the included Gridfinity bin, keeping them organized and always within reach on your workbench.

Why this tool is useful

• Ensures your pen is perfectly centered every time

• No wobble, no misalignment

• Works for a wide range of hole sizes

• Light taper for smooth, accurate centering

• Fully Gridfinity‑compatible

• Fast to print, no supports required

Print Settings

• Material: PLA or PETG

• Layer height: 0.2 mm

• Infill: 20%

• Supports: none needed

• Walls: 2–3 perimeters

If the fit isn't perfect use the xy-hole compensation in your slicer.