This design is to generate simple winding reels to use with a cordless drill. The reel is driven with the mean of a Hex Head Bolt.

The design is parametric and thus fully customizable to fit your needs. To adjust the dimensions, open the FCSTD file with FreeCAD, then the 'Dimensions' spreadsheet in the tree view. You can have both the design and the parameters side by side by clicking on the 'Windows' menu then 'Tile'. The parameters names are self explanatory. If you don't want any Hex Head Insertion cutout set its size or its thickness to 0. For no string holes, set the String Diameter to 0.

Once you are satisfied with your settings, export the new thing in STL. When some parameters combinations are impossible, FreeCAD will either ignore your choice or just crash.

I provide an STL file as example.

This is an open-source design. FreeCAD files are provided.
Feel free to modify this thing at your convenience.

Good design is hard work, even small donations are welcome.