You can use this to mount a 40mm fan for use on socket 7 and socket 370 coolers. Hole pattern and height matches the "standard" 50x50x10 type fan you'll find on small or compact socket 7 and 380 coolers.
You'll need 4 standard type pc fan screws (Smaller head type may be preferable) to mound the fan to the plate, then some longer 15-25 mm screws to mount the plate to the heat sink. (If replacing an existing fan so whatever the cooler came with will probably work)
The corners of the 40mm fan poke out a little from the sides so you may want to check clearance but it probably won't be an issue.
I made this because Noctua does not make a 50mm fan and I'm spoiled on their quiet and effective fans :) Tested with the NF-A4x20 FLX, but should work with any of their 40x10mm or 40x20mm fans.
40_to_50_cpu_fan_adapter.stl | 516.7KB |