function declare as a arrow function, later want to rebind with other object?

Question

let bob = {
   _name: "Bob",
   _friends: ["stackoverflow"],
   printFriends() {
      this._friends.forEach((f)=> {
         console.log(this._name + " knows " + f);
      });
   }
}

its working fine when I call bob.printFriends();

 let bob = {
       _name: "Bob",
       _friends: ["stackoverflow"],
       printFriends() {
          this._friends.forEach((f)=> {
             console.log(this._name + " knows " + f);
          });
       }
    }
bob.printFriends();

but when I change bob object printFriends function to arrow function :

let bob = {
   _name: "Bob",
   _friends: ["stackoverflow"],
   printFriends:()=> {
      this._friends.forEach((f)=> {
         console.log(this._name + " knows " + f);
      });
   }
}

If I do not rebind then this inside the printFriends refer to window object. Thats why I am trying to rebind printFriends

bob.printFriends = bob.printFriends.bind(bob);

then bob.printFriends() is not working as per expectation, giving error: Uncaught TypeError: Cannot read property 'forEach' of undefined at Object.printFriends (:5:19) at :1:5

let bob = {
   _name: "Bob",
   _friends: ["stackoverflow"],
   printFriends:()=> {
      this._friends.forEach((f)=> {
         console.log(this._name + " knows " + f);
      });
   }
}

bob.printFriends = bob.printFriends.bind(bob);
bob.printFriends();