I couldn't find a model for my unknown lineage CNC 3018 that would fit onto the spindle assembly and that could accept my Craftsman shop vac hose so I created this. It is designed to fit on a CNC 3018 with a 42mm diameter spindle motor and a spindle mount that is approx. 58mm wide and for a roughly 31-32mm diameter shop vac hose. Here is the OnShape link if you'd like to make modifications to fit your own CNC. 

Parts list:

• 2 x 3018_Accessory_Mount_M4_v2
• 2 x 3018_Accessory_Mount_M4_Blank_v0
• 1 x 3018_Accessory_Mount_M4_Vac_45deg_V1
• 6 x M4*12mm bolts
• 6 x M4*3mm nuts

Assembly:

• Insert nuts into 3018_Accessory_Mount_M4_v2. 
• Hold one 3018_Accessory_Mount_M4_v2 on the top and the other on the bottom of the spindle. You may have to work this a little bit, I intentionally made it a tight fit.
• Attach the 3018_Accessory_Mount_M4_Blank_v0s and 3018_Accessory_Mount_M4_Vac_45deg_V1 in whatever configuration fits your setup best.

I also used this model to generate a nozzle which fit best for my setup.