I use these in 304. Blind Hole Inch Powertap Cut Taps - GUHRING
But never a tried 1-8 in SS, normally 1/2-20. Don't even know if my lathe would rigid tap a 1-8. These do a nice job of pulling the chips out of the hole. Almost never have any chips left in the hole. If the spec will allow it, try a minor diameter of 0.9219 (59/64) This will give a 50% thread depth, standard for SS.