Tricone drill bit as used in exploration drilling for oil and gas, and minerals, onshore and offshore.

To assemble, first put one cutter cone onto the lug that is attached to the base.
Then assemble the next cutter cone and lug as you slide the lug into the base.
Repeat for the last one.

Optionally 4mm ball bearings may be inserted into the cutter cone through the holes in the lugs, to lock the cutter cones in place. 
Then the holes should be plugged to stop the bbs from falling out.