This chain spool is designed specifically for jewelry chain. Other uses may include: thread, yarn, twine, solder wire, lengths of thin gauge electrical wire, etc.
These spools are also designed to fit perfectly within the drawers of my Storage Cubes (http://www.thingiverse.com/thing:192896).
Design features a cut-away, similar to a shaft key way, where you can place the beginning of the length of material for ease of spooling.
Optimum Infill: 0-5% as these are not load bearing
Optimum Shells: 1 for the inside file and 2 for the outside files
Optimum Layer Height: .25 mm
Print 1 inside file for each outside file. Press fit into each other.
Designing and printing these separately allows for shorter prints as well as the added value of no support material.