from rswww.com

goto: Mechanical, Fasteners/Fixing, Fasteners - Steel, Socket Screws, Hexagon Socket Screws, Cap Head, Zinc Plated Steel
 and then take your pick. you'll have to buy 100 of them unfortunately, but they'll always come in handy! there are other styles of machine screws that RS do, but these are the ones that are most like AC screws.  ;D
i think 12mm long m3 screws will do you, i think the threaded rivets on the APE rads accept about 8-10mm of thread. be careful you don't tighten them into the actual fins of the rad tho, at a push, you could use some washers.

You might have trouble finding anything longer than about 30mm for M3, unless you use M3 threaded rod with nuts & washers.

Are you going to fit a shroud to help eliminate dead spots?

Zitat

ok thank you for that a lot... i think i will have to get longer screws than that you... i measured the papst 120 mm fan i have and that alone is 35mm - including the fan guard - the papst fans need the screw to go through the whole of it to get to the actual thread.

aah sorry, i forgot that these were for the fans!  :-[

RS do do some longer m3 screws:

http://rswww.com/cgi-bin/bv/browse/Modul…toid=-102607831

not as attractive, but 40mm should work!

edit: the other alternative would be to get some shorter srcews, and screw the fans to the rad thru just one of the two lugs at each corner, if you get my meaning? ie, not thru the full 35mm of the fan, just the 3mm or so of the surface touching the rad.