So here is the report I promised in another thread ages ago.
The wheel is done, I went on the first ride with it today. Perfect, not a single glitch, not even as much as a ping from the spokes or noise from the cog.
Parts: ****-man-o XT MTB disc front hub, *****-man-o DX cog drilled, 32 DT Revo spokes (2-1.5-2, crazy light), Mach1 CFX rim, threaded axle, nuts, spacers, bolts.
Total cost: about $70. Posh butted spokes didn't help, but who cares, it's just money
Total weight: 1060 grams including cog, bolts, and axle nuts. 960 w/o cog and its bolts IIRC, still including axle nuts. Not bad.
The wheelbuilding and spacing jobs are relatively straighforward, so I'll skip that. The hub has a ~40mm "chainline", so not a lot of respacing needed if you want 42. I run a 45, which ended up landing the rim almost perfectly in the centre between the two flanges - makes for a nice and strong, laterally stiff wheel.
The cog was not easy to drill... Here it is after I atttacked it freehand, marking the hole places with a pen (BTW, the ISO disc bolts are on a circle of 44mm diameter, which makes the 6 holes exactly 22mm apart from each other, and from the centre as well. 5mm holes needed for the M5 bolts, about 12mm is the ideal bolt length): (You can see that I had already filed off the ridges that hold it on the cassette... They interfere with the XT. Not too hard, a round file and 30 min free time is needed, plus a vise.)
The small dent is all I achieved trying to drill.
I realised this was not gonna work, so I took it to a machinist/mechanic friend who has a drill press. Still no dice. Normal drilll bits won't go through the hardened steel (good job, Shimano...).
In the end, another friend, a mechanic at a railway company who has a massive workshop at his disposal and works with steel every day drilled it with vidia bits (AFAIK thats another name for carbide bits). "Bits" is not a typo... two were ruined in the process. The third achieved final victory. At least his company paid for them
So be prepared that the DX will put up a fight.
I had to correct some holes with a small round file cuz they weren't aligned-surprisingly easy given how hard it was to drill.
Here it is built up:
On the bike:
More pics on my new flickr account: http://www.flickr.com/photos/lofarkas/
Edit: Hmmm, so how do you post flickr images again? I used the URL from the top of the page for the cog pic. I see a red X. I used the address in the "properties" box for the rest, I see the address in text...