I bought a really nice bike trailer I'm so excited to use, but the mounting bracket hole is too small for the axle, and the mounting bracket is made of hardened cast steel. I have a crappy cheap bike trailer that had the same issue, and I was able to widen the hole with a hand drill, but this new one I couldn't make a dent in with a drill press. I need advice.

Can I drill it? If so, how?

Can I mill it or turn it? If so, how?

Does anyone know of a machinist who can do this, or can anyone do this themselves for compensation?

Is it possible to replace this with another one that fits the axle? Or make and adapter that fits the mounting bracket and the axle?

The bike is electric, so the axle contains wires and can't be replaced, as far as I know.

Any advice would be appreciated. I really want to use this.