helicoid pen
thingiverse
a pen, with two springs that revolve around each other. works with a bic ballpoint pen lead (you may have to pass a blade to enlarge the hole a little, or to push hard)
Download Model from thingiverse
With this file you will be able to print helicoid pen with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on helicoid pen.