help hlv-h wiring

I have an hlvh, it has 3 wires on the power cord, each hooked to the 3 poles of the disconnect in the control panel. the second leg has a second wire attached to it that goes to a screw on the panel-that is not shown in the wiring diagram. There does not seem to be a ground wire coming into the machine. Am I overlooking something with the ground, and why is there a wire going from the second leg to a screw on the panel. I found one picture of a machine with a wire on the screw, but cant tell where his wire is coming from.

The lathe has been used in a corner-grounded three phase connection. If you've got a more sensible star/Wye/Neutral grounded setup, or even a wild-leg three phase setup, then it would be good to replace the incoming cable and connect the ground as appropriate to your supply. Expect to use a four or five wire connection, rather than the current three wire connection.

We have 480 out on the ranch irrigation systems and one of the 3 wires coming from the transformers is grounded. Our 240 3phase in the shop is different, all three wires are hot. None of the electrician hooked up irrigation systems use that grounded leg jumped to ground, it seems dangerous in the extreme to me. I am guessing that whoever had the machine before you did a false economy thing to keep from buying a 4 wire cord.

I know I would run a 4 wire cord to the machine and the fourth wire would be a ground. In our shop one of the legs is center tapped to produce 110 to ground I use these to hot leads on the control side of the (L1 and L3) on my lathe. I reverse these to get spindle direction correct. Do not operate the speed change if the spindle does not operate in the correct direction if you do it will lock up the vari-drive and you will have to jump through some hoops to get it to work.
If you do not understand what you are doing, get a qualified electrician's help. Spending a little to get it done correctly could save your life.

Thanks guys, I have 240 single phase supplying an American rotary phase convertor, all my machines are 4 wire, 3 phase and ground. Not seeing a seperate ground wire and that wire jumped off the second post, confused me. I will replace with 4 wire, remove that jumped wired, and run the ground wire to ground post in control box.
Thanks