Interestingly, even after that work, they ended up having to debug a really tricky problem. They sent their gratings to the premier astronomer at Harvard, who reported they weren't "perfect. Eventually this was debugged to a situation where a cam advanced the cutting tool after completing a cutting row, but only occurred when the cable connecting the motor to the tool had a slight bulge due to how the cable was cut and joined.

More fun: http://snl.mit.edu/pub/papers/WP/Nanoruler-White-Paper.pdf