Device Details


This is a customizable (parametric) 3D printable writing aid. The pen ball makes it easier to grip a pen, pencil, or other writing utensil and may be useful for someone who has difficulty holding a pen or pencil directly. The diameter of the ball and the writing utensil diameter are available in different sizing and are able to be customized further if needed.
There are multiple sizes available for this device for both the device size and pen hole size. If you are requesting this device, please indicate which size you believe will work the best for you. There is a printable document that can be used to give a to scale size of the device and pen hole diameter as well as a sizing guide and recommendations below.


A pen or pencil is inserted through the pen ball and is fixed in place by tightening a screw to allow for different pen sizes. The ball is held in the hand with the pen fixed to change the grip to be easier to write with. With different sizing available, this device works well with narrow writing utensils like paintbrushes or wider ones like sharpie markers. In addition, the device itself has alternate sizing to provide options for the user.


Build Instructions

All documentation, design files, and photos can be found on the GitHub page that is linked at the top of this project page. The Maker Checklist document will aid you in following the correct steps to build and work with the requestor.


  • 3D Printing


To assemble the pen ball, you will need:
  • 1x 3D Printed Pen Ball (Top and bottom)
  • 5x M4 machine screws, 20 mm long* ($1.25 – $2.50) Link —or— Alternative Link
  • 5x M4 hex nuts ($0.25)  Link —or— Alternative Link
  • 1x Writing utensil (pen, pencil, etc)

* Note that some printers are less accurate and M4 size hardware may not fit. It is recommended that you go to a hardware store and test different bolt sizes for the pen ball that is created.
* For the Smal Pen Ball, makers can use two M4 x 12mm or 16mm screws for the hardware holding in pen/pencil in place.


  • Screwdriver
  • 3D printer


The design prints in ABS or PLA with no support. 3D print STL’s and instructions can be found on the GitHub page linked at the top of this project page.


The design is parametric, which means that the size of the ball the size of the pen it fits can be modified by changing numbers in OpenSCAD. The editable OpenSCAD file can be found on the GitHub page linked at the top of the project page along with instructions within the documentation.


There are small, medium, and large-sized pen balls available for different hand sizes. In addition, the pen hole diameter can also be changed from narrow, standard, and wide. By use of the set screw, the writing utensil does not need to be the exact size of the pen hole but rather the sizing is available to fit large writing devices like markers and narrow ones such as fine paintbrushes.

pen ball line drawing indicating radius and pen hole size
sizing of Pen Ball device as well as the pen diameter

Pen Ball Sizing Chart:

Pen ball version Pen hole size Ball Diameter (mm) Maximum Pen Hole Diameter (mm)
Small Pen Ball Narrow 50 5
Standard 50 10.5
Wide 50 12.5
Medium Pen Ball Narrow 60 5
Standard 60 10.5
Wide 60 12.5
Large Pen Ball Narrow 70 5
Standard 70 10.5
Wide 70 12.5


Design: Makers Making Change
OpenSCAD: Stewart Russell and Tyler Fentie