This is a simplified version of LEGO part #57520: Technic Tread Sprocket Wheel Small. It has 6 sprockets which fit into the large track treads (like #57518).
I used https://www.thingiverse.com/thing:2859595 as a reference to check dimensions and clearances, but created the part from scratch in Rhino3D (v6).
I printed at 0.15mm layer height and 50% infill. Supports are required.
Note that the center axle is 0.1mm larger in each direction to accomodate printer slop. Tolerances will vary for each printer.