I am trying to wire a milling machine that has a 110/220vac peerless induction motor. It was wired for 110 but that takes 24 amps so I wired it for 220 as per the diagram on the motor but now it runs backward. So my first question is;

Are the two 110 legs that come into my house both A phase or are they A and B phase?

I also found that reversing the starter windings should reverse the direction. I have not tried this yet because I don't know which of the 6 wires are the starter windings. The diagram on the motor is as follows;
For 110v; wires 1,4,5 are connected together and wires 2,3,6 are connected together then both are connected to line current.
For 220v; wires 1,3,5, are connected together and wires 4,6 are connected together. Then wire 2 goes to line and the 4,6 connection goes to line.

The green ground wire was connected to chassis ground and I left it as is.
So my second question:

Is the chassis ground now the return path or am I supposed to hook both 110 legs to either wire 2 or the 4,6 connection and use the other as the neutral?

On a straight 240v motor there is no "return path". It is a line to line circuit. Not a line to neutral circuit.
The ground is the ground, always is, and has nothing to do with the functionality of the circuit.

Is there a wiring diagram on the motor somewhere?

You need a voltage meter, The two legs (alternating breaker spaces in a residential 120/220-240V service) are different phases 180 degrees out of phase with each other. To check whether two live wires are different phases, measuring between them (probe touching each wire) with a voltmeter will be 220-240V in a residential service if they are two different phases, each leg will measure 110-125V to ground or neutral, same phase to same phase reads 1V on many digital voltmeters.

They should NEVER be landed directly on the same spot, like you are asking in your post.

220-240V does not have a neutral. Only a ground wire. No return path is needed, the opposing phases "cancel each other" for lack of a long windy explanation.

Double check the lead numbers wiring diagram, leave #2 connected to one phase (doesn't matter which) and in your motor (you MUST check this with the diagram) usually swapping places with #5 and #6 would reverse at 220V. So;
The remaining #4 and #5 and the other hot (line) would go together;
And #2,#3 and #6 would go together with nothing else.

Should reverse that motor at 220V, but CHECK the wiring diagram