This is a tool for safely removing the feed from a Sheaffer Balance fountain pen, it fits around the feed extension, and should be narrow enough that it won't scratch the inside of the section (especially if you do some post processing).

Cheaper alternative to a tubular brass tool, might be safer too (non marring). Designed for the slender size, but should probably work with standard and oversize too.

Use a feed knockout block and a small hammer if you can, otherwise you can use the inside edge of a thick cardboard roll of sufficient height, like the inside of a masking tape roll or something similar.

Printed in PLA+ with 100% infill, 0.4mm nozzle and 0.2mm layer height.

Print the head of it facing the buildplate.