Where to ground the lead wire air compressor

Hello, first time poster here and first i would like to thank anyone who responds to my question. 

I’m wiring up my air compressor and i am running into a quick question. Typically i always see a lug to bolt the ground to but i dont see an avail ground lug here that is unused. Should i ground it to the larger green cable that is already grounded to the box( see  image 1502 pic). Or should i ground it to the bolt that is above the smaller ground in the pic( see image 1504)? 

 

Any input would be greatly appreciated in advance!!!

 

Specs

7.5 hp schulz air compressor 240v single phase. 

Welcome to the forum.

 

All of those locations are already electrically connected and electrically identical.

 

There are regulations about stacking ground connections, including things like washers and locking washers.

 

Always follow the manufacturer’s instructions.

 

The simplest correct thing to do is to scrape away paint from a different existing threaded hole, not disturbing existing correctly wired and correctly connected grounds. Wrap the twisted (assuming stranded) wire clockwise around the new ground screw. My suggestion would be to have a correct (same size) flat washer, then an external star lock washer, then the screw head, ensuring the screw length permits at least two full threads of penetration into the metal and ensuring the hole depth doesn’t prevent proper tightening. Don’t over tighten.