I wonder how accurately I will have to work if I make a wooden burr puzzle out of square sticks as for example described in http://en.wikipedia.org/wiki/Burr_puzzle. Should the notches be exactly the width of the square sticks so that everything fits tight together or should I sand down the sticks a little or widen the notches so the pieces will work easily together? Does anybody have experiences with that?
I have a copy of this particular wooden burr puzzle. The main thing to watch out for (and not just with this burr) is not actually the width of the internal pieces, but the precision of the angle of the cuts.
If you're making this using high-precision tools, then just make sure everything is squared properly. And you'll probably be fine.
If you are, however, having problems assembling it, look for places that don't quite fit together well under tension and sand those down specifically. With this puzzle, since the pieces are large, it's hard to sand too much, but on future burrs be careful with this. Just don't take off much and you should be fine.
I'd recommend against sanding everywhere, though. It risks making the puzzle too loose.
For puzzle and precision longevity, I would also suggest using harder woods. I have a few of these puzzles from olive wood and they're too soft (feel like lime/linden). If you're not careful while solving them, it's easy to damage the vertices. After several runs, the starting precision matters little.
For tips on super-precise wooden puzzlemaking, check out this tutorial from Lee Krasnow, one of the masters of puzzlecrafting:
http://www.instructables.com/id/Precision-Puzzlemaking-Primer----Volume-1/
