I have modified it so much I renamed it  " FrankenDoodle "

Make sure your bolt hasn't worn the hole in the  pulleys too much or when you tighten set screws the pulleys will rotate in an eccentric circle and have a lot  run out. This will mess with belt tension big time if wear is extensive ( 1/8 in ) . That is why I used a drill press with a 5/16 drill bit to bore out the holes and installed bearings into pulleys they fit nice and tight on bolt and in pulleys . No run out at all and very smooth rolling. Hope this helps .

PS:  this also works great  on the Y axis pulley , you may have to file the top of the pulley for clearance if you use Lawsy's carriages with bearings. 

PSS:  I used these front blocks they work great found on Thingiverse  They use all the original hardware and holes

http://www.thingiverse.com/thing:114554
Solidoodle Y-Axis Bracket by Wompus
Published on July 8, 2013

thats the set I printed for my future upgrades. where did ya get those pulleys? metal looks lots better than the plastic ones that came on my SD2 and not quite as tall of shoulders too

PS:  this also works great  on the Y axis pulley , you may have to file the top of the pulley for clearance if you use Lawsy's carriages with bearings. 

PSS:  I used these front blocks they work great found on Thingiverse  They use all the original hardware and holes

http://www.thingiverse.com/thing:114554
Solidoodle Y-Axis Bracket by Wompus
Published on July 8, 2013

Slimstar's method is potentially superior if you're willing/equipped to bore the pulleys themselves (I'd recommend a lathe, but looks like you can get away with a drill press).

satman, try again, but drill out the shaft hole slowly and carefully with an 8mm drill bit before you drive the shafts in. If you're doing it in the case, please be extra careful as I received a really nasty cut to the top of my thumb from the solidoodle case when pulling a shaft out of one of these.

I modified these a little to get rid of the keyhole shape, leave a plain bore, and got rid of the flange (as I was shipped plain bearings not flanged). I'll find where I left the files and see if I can stick them here or tv for you.

OK n2, on an SD3 the pulleys do not have bearings. Nor bushings. The aluminium bore of the pulley runs against the shank of the M5 bolt. You can probably work out what happens after a while. They run much nicer (and don't wear out) when you lock the pulley to the bolt and get the bolt spinning on these bearings.