My ultimaker suffered from the problems outlined in the ultimaker wiki with the loose holes on the delrin plastic blocks that the springy bed mounts on. The holes were so loose that one stripped. I measured the old one, drew it up, and printed. voila!
A bit of a hack job; 2 problems: My printer shrinks holes - not sure if its the skein (Cura RC1) or calibration on the printer...and the model is about 3% too big to EASILY pop it into the wood, so I printed it at 95% rather than resizing the model (because the model is afaik the correct per my measurements).
Because of the shrinkyholes and the 'print at 95%', I had to make the center bore larger than it should be (almost 3.4mm) and it comes off the printer at around 2.8mm diameter - just small enough for the screw teeth to have something to bite into.
-- they suggest putting a piece of paper down the bore with the screw - I figured since I have a 3d printer, do it properly!
Long story short:
"Screwblock Large.stl" the one I use, 3rd on the right in the picture of 3
ABS (pla should be fine)
2 walls @ .4mm nozzle (more is fine just they won't fit, ymmv).
"Screwblock original.stl" middle in the picture of 3
same settings, but you'll have to sand a few thou off the outside edges for it to fit in the machine, and maybe ream out the hole - depends on your printer.