Small Cord Spool

In honor of FreeCAD's imminent 1.0 release, I'm putting out this parametric design for a spool for small cords like 95 lb paracord, micro-cord, bankline, and mason's line.  Spools are great for fast re-winding.  This spool is designed to be lightweight.  Print two identical copies of the spool half, and snap them together using the alignment holes (teardrop shaped) to get them positioned.  Print two shafts to aid in winding.  One goes through the central hole, and the other (in the opposite direction) through an adjacent hole.  There are square holes in the “barrel” to start the cord, and the teardrop holes on the edge can be used to secure the cord when done.

Modification

The most important parameters can be set in the spreadsheet, and the model will automatically adjust.  These include:

• central hole diameter.  I like 11mm because it will fit pens/markers that I commonly carry. 18mm is good for finger winding.  This effectively sets the inner spool diameter.
• outer spool diameter: the… um… outer diameter of the spool.
• spool width; this is the inner width, the side-to-side space for cord.
• wall thickness.  I like 1mm for smaller spools and 1.2 for bigger ones.  This is pretty flexible, and possibly breakable, but I'm willing to risk it for light and bendy.  The spool is a luxury in the field and I can live without it.
• minimum web thickness.  This is the smallest distance between two holes, or holes and the edge.  This does not include the teardrop alignment holes.  Those can be closer.
• alignment hole diameter.  This is the size of the teardrop holes.  These are for helping align the two halves, and can also be used to secure the end of the cord.  Spool alignment is purely aesthetic, but I like the outer holes to align.

The size, number, and placement of the outer holes (just there for weight reduction) are determined automatically according to the minimum web thickness.

The spreadsheet includes (at the right) some suggested parameters for about 100ft (30m) of cord of two different types.  Just copy/paste those six numbers over to the left.  Or, you can save your own settings there for future recall.  At the bottom of the spreadsheet, there's a section for estimating the amount of cord that will fit on the spool.  It currently assumes 80% packing density (loose and sloppy winding), but you can set that.

Printing

I've printed mine in PLA.  No supports are required anywhere.  I use 10% infill, but realistically, there's almost no interior volume anyway… just a tiny bit in the shafts.  I just print one pair of shafts for my widest spool (the shaft is 24mm longer than the spool is wide) and use those for all my spools.  I have had minor adhesion problems (maybe 60% yield) on the shafts, but I don't use a brim because I'd rather have it clean and smooth and I can just write off a failure here and there.