A complete redesign of a Gridfinity block I found on Printables by LutaVulgaris - the original was kitbashed from an existing wire holder and a plain gridfinity base. My version is designed from scratch to optimise material use and to run smoothly (the spool spins freely even printed on my 0.6mm nozzle)
The spool is designed to use 3mm heated inserts and 3mm x 8mm countersunk machine screws, but a standard screw might work as well - I designed my own spool as it seems like every spool of wire I buy on Amazon comes with a different size (quick tip for re-spooling wire - the screw attachment on the spool allows you to spin it with a power drill, especially if using hex drive machine screws). If you want to design your own spool mandrels, a simple rod with a radius of 8mm and a length of approx 37.5mm can be used.
Although I designed this for my own use I take extra time to ensure that my models are easily printed by others and often print several iterations during this process, if you make use of any of my models, please consider buying me a coffee to fuel future projects :)