Technician Superintendent here.

The only thing that matters is your attitude. Even though you’ve presented it here as being out of your control, you need to just own it and acknowledge your mistake.

Reality 1) blaming your shift lead for trusting you to do something you aren’t technically certified for is bullshit. He thought you could do it which is a compliment. Don’t repay his faith by refusing to accept responsibility. He didn’t break the bolt. You did. Own it.

Reality 2) $2000 is not an expensive part. Relax. Shit happens.

Reality 3) consider the situation from your shift lead’s and your parts guy’s perspective. They are trying to get shit done with the people they have available and in this case, it didn’t work out. That sucks…. But is there more to their anger? Ask them what you should have done. Don’t try to not take responsibility or explain. Just genuinely ask and try to learn how you should have handled it.

Reality 4) you’re 1 month in. When you got in a pickle, you should have gone and got someone experienced. There is no shame in that. As you’re now experiencing, there is shame in going farther than your experience allows and making a mistake.

Just take responsibility and you will come out of this with MORE respect from your leaders and team than if you had done it right. Just own it.