blown fuse

I hate to ask but I know very little about electricity and didn't find my answere in my search.
I am running my lights from a fuse box and regardless of the size fuse used in blows when the headlight switch is pulled on (most of the time). I've traced my wires about three times and all seems correct. wiring is grounded to the body as is the neg. side of the battery.
It appears that the switch - I've tried two with the same results - is causing a direct short at the dash. Should a switch ground itself to the dash? Could I possibly have two faulty switches? One switch is EOM and both are metal cased. Should I go buy a newer plastic cased switch? Is there something else you can think of that I may or may not have done?
Thanks for carrying me thru this.
Tommy

 

Remove the switch from the dash, leave all wires attached and try it again. Altho the switch contacts inside are insulated from case, there may be something else going on. The OEM switch should have a circuit breaker instead of fuse.