So here's yet another cut of transforming empty spool holders into parts drawers!! This version builds on the ideas others have already submitted but with a few extra features:

Lockable & Secure: Simple locking bar holds drawers closed
Drawers pivot on short length of 1.75 mm filament eliminating need for long screws
Stackable - the feet of each assembly engages with the pivot screws of one below it!
Drawer-dividers can be added or removed as needed

This design works best with HATCHBOX spools (Drawing Attached). HATCHBOX spools are heavy duty and have solid sides and a nice hole pattern that works well for easy drawer assembly. The spool hole pattern also allows the drawer-locking feature to nicely engage with the top of the spool.

ASSEMBLY NOTES: As show in the assembly drawing details, a short length of 1.75mm filament is used as the PIVOT AXLE for each three-drawer-stackup. The top and bottom drawers of each stack-up are attached with short (8-12mm long) M3 or 4-40 screws. Just tap each top and bottom drawer pivot hole a short distance to accept the screws you use.

The locking/latching bar is made from a short length of 1.75 mm dia filament. A short length of piano-wire (or common coat-hanger wire) may be used if you want a more rigid locking mechanism.

CAUTION: Spool dimensions vary! Be sure to measure the empty spools you are planning to use and compare outer and hub diameters as well as the spool width measurements to the dimensions shown on the SPOOL drawing. This design was optimized for HATCHBOX sized spools and may not work well with other spools sizes!

STACKING: Drawer-Spool assemblies may be readily stacked one on top of another as the BOTTOM PIVOT bushing captures the machine screw-heads of the Drawer-Spool assembly below it. This makes a stack of 2 or more drawer assemblies very stable.