Modeling advice needed

So I’m modeling Jinx’s grenade from arcane, and I’m struggling to figure out how I’d go about modeling this piece here

also, how would I go about modeling the shark teeth on the model

Any help would be appreciated. Thanks, guys!

For the teeth, I’d start with a low-poly cylinder, cut it in half, move some of the vertices around and cut around with the knife tool:

Ahh it’s a simpler method than expected thank you so much!
Do you have any advice on modeling the circled part in the first photo as well?

for the skrew part, there should be an addon ( Bolt Factory, probably, shipped with blender).

I’m talking about the part it’s screwed into

Build it up from basic shapes, booleaned together and cleaned up?