Teddy Talk: Creating, Collecting, Connecting

Thank you

I'm very new to teddy making and had a question about putting the bear together. I started with thread crochet bears so I was thread jointing them. I just tried crocheting one with eyelash yarn, so he is bigger. I am happy with his out come, and I thread jointed him using thread. Although it worked, I'm afraid it's not sturdy enough to last long. ( specially in a house with 7 children ) I read about cotter pins, lock nuts and a few other things. I am wondering what the best way to put them together is when they are crocheted bigger, and explain how to use these other ways? Thank you for the help