The des_crft_aparts.2da file is the .2da file that defines the DCs and (relative) gold piece costs for modifying armor with the craft armor skill.
This file is used by the scriptsx2_im_getcostdc, x2_im_nextpart, and x2_im_prevpart, which are invoked by the dialogx0_skill_ctrap.
Columns of des_crft_aparts.2da
ID (no actual name)
Row numbers for the benefit of human readers. The game engine ignores the value in this field, instead generating sequential row numbers as the file is read. It is good practice to keep the entries in this field sequentially numbered to avoid confusion.
The name of the armor part for the benefit of human readers. This is ignored by the game.
The number of variants for the armor part.
The percentage of the item's value that is charged for modifying this part.
The increase in craft armor DC when this part is changed. This does not stack with other parts; only the highest DC increase is used when multiple parts are changed.