A replacement spindle for 3mm spools that have a 54mm hole in the middle. (UltiMachine & Makerbot 1kg spools)I made this to replace the BfB spindle for different size spools of 3mm filament. This fits the Ultimachine spools (54 mm hole in the middle) and Makerbot 1Kg spools as well. first, you will need to print the base from http://www.thingiverse.com/thing:26205, then print my top & bottom.I printed them with 0.5mm resolution, 50% fill, a couple of extra skins. the bearing in the middle is a 8x22x7 skateboard bearing, standard in the US. The guy at the skateboard shop just gave me one. (Shout out to Skate Works of Los Altos, CA! Thanks!) Snap in the bearing, and glue in the bottom and top. you'll need a 6mm allen wrench to change the spindle in the printer, and you need to lift it up to get the nut back on the screw. (remember to put the spacer back, or no turning for you.) I uploaded the STEP files, like valentFx. If anyone needs another format, let me know. I did this with Autodesk 123D, and it supports a pile of formats. (sorry, not SCAD. )