30mm fan mount for the E3D style heatsink available on eBay.This heatsink is designed to sit flush with the bottom fin on the heatsink.
The E3D style heatsink is 50mm tall by ~25mm dia by ~32mm from on the outer edges of the fins and has 10 fins.
Designed to fit a BullDog Lite extruder on either stock mount or the lovely design by ooznest. Also designed so it can easily removed as I found the Bulldog a particularly painful extruder to work with. Simply search for Ooznest to see the rest of their work and get the X Axis carriage to go with this.
Okay, I've printed this reliably at 0.25mm/50%/3x shells and normal res. The shells are more important then the fill as there is little volumes really to fill.
Print this with the fan mount as it is in the STL. If you print it orientated flat, the 4 shafts for the fan bolts/ screws will be parallel with the layers. If you try cutting a thread into this, the layers will just split. Clamping the print gently between a couple of pieces of wood before cutting a thread.
After printing the piece, use a 2.5mm drill to tidy the 4 shafts. Just twisting the drill bit with your fingers will be enough.
I suggest strongly that the piece is fumed in acetone to toughen it up, make it look better and make it easier to fit the heatsink. Leave the piece fuming until the sides have smoothed out and the edges have started to go transparent. Remove the piece and whilst it is still soft from the acetone, lightly squeeze the sides and slide the heatsink in and out until you are happy with the movement. Leave the heatsink in the piece overnight until the ABS has hardened again. You will still probably need to work the heatsink back and forth a few times to loosen it up.
Now if you have printed the piece horizontally, clamp it lightly between wood before cutting a 3mm thread into the shafts or putting a self tapper screw in a couple of times.
The shafts for the screws/bolts are 12mm deep which means 8mm actual. Typical 3mm thread cutters have about 2-4mm lead in to guide cutting. Add 10mm for the thickness of a typical 30mm fan, you end up able to use 3mm 16 or 3mm 20 bolts.
To secure the fan mount on the heatsink use man's best friend, move over Rover, a zip tie. Surprisingly little tension on the zip tie is needed to lock the fan mount solid.
HINTS ON ACETONE FUMING
I use a 1.75L pasta/ cereal tupperware container. A piece of metal flywire sits about 1/3 down. I just chuck in 30ml of cold acetone and this way I can be quite accurate on how long it takes to fume different pieces.
If you are thinking about trying hot acetone fuming, seriously consider not doing it.